No strategy is foolproof. Since odds tend to even out over time, the house still has an edge. Even if you place bets on half the board, you're still more likely to lose money over time. Additionally, there's no guarantee that the ball won't land on a number between 1 and 12 several times in a row.

A roulette system that carries relatively little risk is the red bet  system. You bet a small amount on red and double it every time the ball does not fall on a red colour until you make a profit. In addition, you always bet the minimum amount on black and double it when the ball falls on 0  (or 00 ).