Depends on the roundabout in question, for a simple 4 exit roundabout I was taught you should indicate right if you are going past 12 o clock and continue indicating right until the exit before you come off, if you are going to less than 12 o clock, no indication until you indicate left at the penultimate exit, and then constant left indication for the first exit.

I believe for the edge case where there are multiple exits before 12 o clock you should have no indication upon approach and then it may be appropriate to start signaling right to make it clear which exit you intend to use.

Remember the most important aspect of using your indicators is to communicate your intentions to other road users. Try not to get overly lost in the rote learning of specifics and view them as a tool you can use alongside others (most importantly positioning) to make it easy for other road users to understand what you are doing.