Take a look at this info on roulette house edge. I found it really helpful.

You can calculate the roulette house edge to play the game online by subtracting the theoretical payment without the house edge from the actual payoff that is publicized in the casino. Multiply this figure with the mathematical probability of gaining your bet. Multiply the sum further by 100 to arrive at the percentage house edge.

For instance, in American Roulette there are 38 pockets on the wheel (36 numbers and 2 zero pockets). If the casino payoff is 1:35, the probability of your winning is 1:37. Thus, we calculate the house edge as: [37/1 - 35/1] x 1/38 x 100 = 5.263%.

If this is the case with European Roulette, there are 37 pockets on the wheel (36 numbers and a zero pocket). If the casino payoff is 1:35, the probability of you winning is 1:36. The house edge is calculated as: [36/1 - 35/1] x 1/37 x 100 = 2.703%.

The above analysis is a pointer to always go for European Roulette unless you especially like wagering on the 00 pocket.

The house in roulette has the same edge on all other kinds of bets, because the payouts are set as if the zero square(s) did not exist. The only exclusion are the 5 numbers bet where the house edge is substantially greater (7.89% on the American wheel) and the 'even money' bets in some of the European roulette games, where it is halved because half the stake is lost when a zero comes up.