While there is no strategy that can guarantee a profit in the long run when playing roulette, the Martingale betting system is often regarded as the most successful strategy.
Some bets in American Roulette have an even higher house edge than the 5.26% average. For example, a bet on the Five Numbers (0, 00, 1, 2, 3) carries a house edge of 7.89%. Outside bets in roulette carry the lowest risk. They cover more numbers yet the payouts are lower (1/1 for Red, Black, Odd, Even, 1 18, 19 36).