From what I know french roulette is just another variation of roulette which became popular after the French revolution. Other than that, I don't think there is much difference in the way the game is played.
I thought the French, like most European casinos played with a single zero, while the American casinos tend to have 0 and 00 pockets. It means the house edge is slightly less and the players get slightly better odds (36 not 37). I thought there was something different about the table layouts for the two games, but I'm not sure. It's not my game.
Thanks for the replies guys. It gives me some idea of what the difference is and where I can do some more research. I'm really interested to know the difference in the rules and what that means for me as a player.