While an extremely rare occurrence, a number appearing four times in a row is not necessarily indicative of a wheel bias neither in landbased or online roulette. Bias cannot be identified with small sample size, you need thousands of spins to arrive at any reasonable conclusions. Also, it is in the online casinos' best interest to ensure their RNGs produce random results for two purposes.
First, randomness guarantees the casino collects its expected percentage in profits from the games. Second, if an operator is caught using rigged software during an RNG audit, it will lose both its reputation and its license.