If you haven't driven in France, your view of roundabouts might have a Hollywood "play it for laughs" flavour. You know, put Chevy Chase in a car and have him drive around and around and around the Arc de Triomphe for hours. Real funny, eh?
Reality is very different. Roundabouts mean fewer STOP signs (and they do say STOP in France - not ARRET as in Quebec), traffic flows pretty well, not a lot of speeding (why bother when there's another roundabout in a few klics?) and far fewer wrong turns.
Aside from the "A" series of highways - controlled access toll routes like thruways in the U.S. or the beloved 407 in Ontario - roundabouts are found everywhere around here - there's even one on the slopes of Mt. Ventoux - except in Carpentras, as noted elsewhere.
Priority goes to someone who is already on the roundabout, so jump in when there's nothing on your left. It is preferable to be on the outside lane for easier exit, but sometimes that isn't possible. I always check my rear-view mirror as I am exiting a roundabout to make sure I'm not cutting somebody off.
If we're not sure which exit to take I'll do a 360. I have even been known to do a 720, until my navigator & I are sure. If, even then, we discover we've made a wrong decision, no problem - I'll just swing around at the next roundabout & do it again.
Our companions are very impressed by the roundabouts here in the south of France.
I call them "stress reducers" - love 'em.