I like this roundabout style as it gives flexibility on what direction to send my oxides for further refining. And it is fun watching the oxides chase each around the ring.

This guide was created with version 0.99.11

Multi-Regolith Refinery
Belt 1 (Belt 2 recommended)
Small bulk storage (Large bulk storage recommended)
Belt Undergrounding
Programmable Splitters

Layout

The lighter colored belts are the T2 belts. You can make the loop tighter if you like. I just like having some room if I need to change things up later.

Merging Traffic

The most important step is to configure your splitters on the outer belt. You need to make sure the items on the belt have priority. Just like traffic on a roundabout. Click on each splitter and give the input from the direction of travel high priority (three chevrons). Leave the other input and the output at normal priority. The red arrows show the direction of travel on the belt.

Off-Ramp
When you connect a belt to pull oxides off the roundabout, remember to configure it with the oxide you want to output. You do not need to adjust the priority on this splitter. But you should upgrade to T2 so it does not slow the roundabout down.


Notes
The number of inputs coming in can be reduced to one on either side. As you get higher tier belts and upgrade the MRRs you will need more regolith to keep up with the refineries.

The slag can be outputted to either side, just switch the belts up.

Oxides can be pulled from the outer belt in any direction. Making it agnostic on how the rest of your production chain is setup.

I hope you found this helpful. My first time creating a guide. Feel free to leave any feedback :)

And thank you to the dev team for making a great game!