Martingale would be a profitable strategy if the following conditions were met: You and the casino have an infinite bankroll, the casino has no betting limits, you got to choose when to stop playing. This is the real world however so the system is completely flawed and will fail.
There is no system to "beat roulette" unless as was already indicated the wheel is biased. Most casinos monitor this. If by chance you found a wheel that was biased and the casino did not know about it there is little chance you could make much from it as almost every modern casino is aware of bias in roulette wheels and would act accordingly to stop you from wagering even if they did not actively monitor the wheel as your bets would be triggered as an anomaly.
The only hope in hell you have of making any money is playing at a european table (2.70% vs. 5.26% American) and running on the good side of variance. If you managed this stop playing forever while ahead and count yourself lucky.
There is no system to "beat roulette" unless as was already indicated the wheel is biased. Most casinos monitor this. If by chance you found a wheel that was biased and the casino did not know about it there is little chance you could make much from it as almost every modern casino is aware of bias in roulette wheels and would act accordingly to stop you from wagering even if they did not actively monitor the wheel as your bets would be triggered as an anomaly.
The only hope in hell you have of making any money is playing at a european table (2.70% vs. 5.26% American) and running on the good side of variance. If you managed this stop playing forever while ahead and count yourself lucky.