The quick answer is no, it is not. Roulette isn't rigged online for the same reason that the game isn't rigged in person, the casino doesn't need to rig the game to make their money! Double zero roulette, by far the most common version of the game being played today, has a built-in house advantage of just over 5%.
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. It is easy to use and can provide good returns.