Up until the 70s/80s the French weren't that big on roundabouts - now they've gone mental with them and install them at every opportunity.
There are 2 problems with this;
1. Many French drivers weren't taught how to use roundabouts as they hardly existed when they learned to drive.
2. The majority of roundabouts, especially in town, have no signs beforehand to tell you what's happening, so unless you're familiar with a specific roundabout or are using a GPS, there's absolutely no way of knowing what lane you're meant to be in.