Player Roles are the way you, as a team, position yourself differently throughout the map in order to have a solid defense and counter stratting (CT Side) or the way you're going to position yourself and work together in the map in order to make it through to one of the bombsites (T Side).
This guide will explain exactly how to manage and tell your team how to win in counter-strike global offensive. This time i'll be focusing on the map de_inferno, which is personally my favourite map.
If you follow this guide I can guarantee you will win.

There are alot of different names for each role in CS, but after researching and giving this idea alot of thought i've came up with the ones that I think are the most ideal and easy to understand.

CT Side

• Anchors
  
• Rotators
  
• Playmakers

T Side

• Entry Fraggers
  
• Playmakers
  
• Support
  
• AWPers
  
• Lurkers

Like i mentioned before , on the CT Side there are 3 main roles: Anchors, Rotators and Playmakers.

Anchors

You should have 2 anchors:

• 1 playing dedicated B Site
  
• 1 playing dedicated pit A Site

These players NEVER leave the site they're playing in, untill they're 100% SURE that the bomb is heading the other way. They're the most important players on the CT Side cause they allow their teammates to get frags and help somewhere else cause they know these players are holding the sites regardless.
These players should stay very calm cause they're eventually going to deal with alot of terrorists alone and they should be very communicative to the team so they can rotate properly, depending on the information given.

B Player
Pro Players that have this role: Krimz, Friberg,Neo,NBK.

The B anchor should play from the site itself while the other guy should play CT Spawn which allows him to rotate to A if needed.
The B anchor needs to have clever position, he needs to save his smoke as long as he can, delaying the rush from the terrorist.
Like i said , he's the last guy to abandon B if it seems like the terrorist are executing towards A, cause they can fake and then the B site is wide open, and you don't want that to happen.
If it's mid round in a 3v3 situation, the CT's should play with 2 in A and 1 B (anchor), if he knows that they're pushing banana, his job isn't to try to spray them and get as most kills as he can. Although that seems like a good idea, if they kill him, the terrorist have the site in a 3v2 situation with the bomb planted and it's extremely hard to win that round as CT's.
So what the B anchor should do is hide and try to get 1 free kill. Good places to hide are either dark, or tribox. Tribox is an amazing spot, cause in order for them to kill you they have to wrap the entire site to get to you. By the time you know it's B you just hide there or dark, and you tell your team it's B, but be detailed about it, tell them if they're still banana or they're already in site so they can rotate the spawn or even flank banana. The B anchor needs to stay alive as most as he can and get one free frag by the time they're up close to him.

adreN from liquid has a really helpful video explaining this role in B, check it out if you want to know even more details:











Pit A Site Player
Pro Players that have this role: f0rest, shroud, edward, shox

The A anchor should play 95% of the times from pit. The one time you don't want to stay there is if they catch up and start doing execute smoke/molotov's strats to block you off. If they do that you want to be creative and unpredictable and go to a spot like graveyard or balcony.
Like the B anchor, this guy's job is to stay alive. The A Anchor can also support the long/short guy with some flashes and be a support player in that sense, but he should save his smoke for as long as he can untill he knows that they're rushing him. He is the last guy to rotate to B as well, for obvious reasons.
If you hide in the corner of pit in a 3v3 situation where they're rushing you, you have a very high chance of winning the round. You wait untill they're actually in site and you tell your team what's the happening. Pay attention to the footsteps and you can catch someone off guard and then force them to rush you, by the time they rush you, your team mates already rotated from B and can kill them while they're jumping pit to kill you.


Rotators
Pro Players that have this role: Happy, GeT_RiGhT, olofmeister, snax

You should always have a guy playing this role. This guys' job is to play off their teammates, to help B site with grenades and to rotate to A if needed and leave the B anchor there.
This player throws the first smokes and flashes to hold them in B, so the B Anchor can save his to hold a push later in the round.
This is a position where you don't need alot of communication yourself but you need to be very aware of your teammates's calls. If they need help in A, your job is to go long and to coordenate a crossfire or some good positions with the players left in A. Even though playing from site, seems like a good idea to hold A off, you should probably stay in long cause your B Anchor might need your help.
The Rotator usually plays CT Spawn towards B. This player should give priority to utilities (grenades) instead of fire weapons.

Playmakers

You should have 2 Playmakers:

• 1 playing short/lane side
  
• 1 playing long side

These players usually do well by having really good crossfires in middle and occasionally peeking mid and getting frags. Most pro players defending these positions have coordinated flash peeks and they time well their smokes
Pro Players that have this role: allu & xizt, pashabiceps & byali, flusha & jw, kioshima & smithz

As a Playmaker, your job is to get entries from the CT's in mid ,damage them with grenades and use properly the smokes along with your teammate to hold A as most as possible.
Either long or short, this is also the ideal position to have an AWP cause it's almost guaranteed you'll get an entry frag in mid if you time it well.
These player's jobs are to get a kill and fall back and play safe a 5v4 with your team, not be a hero and repeek and eventually dying, making it a 4v4.
The short player should help the A anchor if they rush balcony and to be aware of the boiler room too. After getting a kill, a passive position to take is falling back to site and crossfiring with your A anchor balcony & short.
The long player should fall back to either library or archway after getting the first kill. He's also the first player that is going to rotate in case help is required in the B Site.
Pro Tip: Don't go in the cubby, unless you're playing 2 long. It's an easy spot to molotov and terrorists have the peekers advantage when rushing you.
Both these players should prioritize fire weapons instead of grenades, but a smoke is also required.

First of all, there are 5 different roles that one can have on the T Side.

Entry Fragger
Pro Players that have this role: Friberg, Kioshima, dupreeh,flusha

Like the name says, this player is the first one in, he's agressive and his job is either to get the first frag of the round to the terrorists, or to do have a ton of initial damage. If he dies, his job is to have perfect communication to tell shortly and precisely where the CT's are playing so they can trade the frag. This player should have great aim and great frag ability overall and communication should be perfect.
This player usually plays in banana, along with the Playmaker to get early control of it and trying to get the first kills, helping his team tremendously.
Pro tip: The entry frag should play on a slightly higher sensivity to react to the multiple angles he's going to expose himself while pushing to the site.

Playmaker
Pro Players that have this role: Forest, device, olofmeister, NBK

These player's roles are to help taking control of the map, with the Entry Fragger, and his job is to instantly get a trade kill if the Entry Fragger dies. A Playmaker, he's an agressive player, should have really good aim, and he's usually a clutch player as well.
He's the guy that when the team is down on men, goes for those crazy plays to open up the site and give his team a chance to win that round.
He also plays either banana or mid trying to get early frags for the team.

Support
Pro Players that have this role: Krimz, Xizt, Ex6tenz, Xyp9x

This is the guy that is going to help the ones who need a pop flash or a smoke. He should have great knowledge of the map and nades, he should have the ability to stay calm and trade the frags needed mid round.
This guy is usually the last guy to rush to a site, he usually plays bottom mid or second mid trying to get his team mates further in the map and getting control of the map.

Awper
Pro Players that have this role: KennyS, GuardiaN, JW, allu

As the name implies, he's the primary awp, he should have great reaction time and aim. Should have the ability to entry and great communication.
Instead of playing of the nades to get the control of the map with the entry fraggers, your team can set up an awper holding a position.
This is the guy that can just run to a position and get an easy entry kill, usually mid or banana.
Some teams choose to make their playstyle around him like Titan for instance, and others just have him as one more man with a powerful fireweapon like fnatic.

Lurker
Pro Players that have this role: GeT_RiGhT, Happy, Maniac, swag

This is your wild card. If your plan is to go A , this guy is in B or the other way around.
He's unpredictable to keep the enemies on their toes, should have great knowledge of rotations, great positioning and use of sound.
He usually plays in apps, waiting for someone to rush or to flank them later if his team starts executing towards B. His job is to go behind the enemies and catch them off guard by positioning himself in the opposite side of where his team mates are.

Strat Caller
Pro Players that have this role: pronax, Happy, Ex6tenz, Neo

I didn't mention this one before because it's not really a position you take in game , it's more like a role but communication wise.
This is the leader, he calls the round strategies, obviously should have great knowledge in the game.

I also want to point out that communication is a must for every team at every position. The better your shot, the better you'll be at your respective role (obviously). These "roles" are not official, and I'm sure there are many more that could be described. I will cover more on this later.

I hope you learned something from this, maybe it helped you find your own role and feel more comfortable about it or you decided to implement this system in your own team. Either way i'm sure you're going to succeed.
I might write a similar guide about other competitive maps depending on the feedback i get in this one.
Thank you for reading this and good luck :)