Them roundabouts be weird. I think I learned a few years ago that you're not supposed to change lanes while in the roundabout, generally, if it's like 2 lanes or less -- get into the right lane before entering the roundabout. Best part is they work when the power goes out.
Of course you are allowed to change lanes. Especially on the larger ones. You are even supposed to change lanes. A good rotonde/roundabout/rotary/circle can have 3 or even 4 lanes. Great fun.
Suppose you need to go 3/4 around. You are then supposed to go immediately to the interior lane when you enter the roundabout. Then while driving, you should slowly "fan out". By the time you are approaching your exit, you should be at the most exterior lane.
Look at the blue line in this picture:
When I took my drivers-lessons, I used to live 200 meters from a large roundabout (3-4 lanes, 6 exits). I love roundabouts. The real fun ones are the roundabouts that have different rules of preference ! Normally "people from the right" have preference (in my country). But on roundabouts they changed that. Once you are on, you have the right-of-way. And the newcomers have to stop. But there are some very old roundabouts in my country, where the old rule holds true. On those roundabouts the newcomers, who come from the right, have right of way. And the people on the roundabout have to stop. These roundabouts have lights at the entrances, or else the roundabout could get congested easily. (It still happens a few times per year). I think we have only a few of these left in my country.
I guess they have the same situations in France too. Paris has lots of crazy roundabouts too.
This one also seems great fun:
https://en.wikipedia.org/wiki/Magic_Roundabout_(Swindon)
I love roundabouts. I don't mind driving a few extra rounds when traffic is really heavy. Just for fun.