Roulette is a pure luck game and no strategy exist for it unless you try martingale and back to base bet strategies like dice.
In Casinos there are actually people who try and do martingale. And you can easily see their face turning red, when they lost like 6-7 times in a row. Most eventually walk away and the next roll would of been a winner for them.
if you like bet using martingale strategy, you can try bet in low (1 to 18) or high (19 to 36) sometimes it's working fine. i've try before i share this strategy.