The Kelly Criterion is a mathematical formula used to determine the optimal bet size based on your perceived edge over the game. In online Roulette, you would first estimate your probability of winning for a particular bet and the odds being offered. The formula calculates the fraction of your bankroll to wager by taking the difference between the probability of winning and the probability of losing, divided by the odds. While applying the Kelly Criterion can help manage your bankroll more effectively, it’s important to remember that Roulette outcomes are inherently random, and using this method does not guarantee winnings. Adjusting the bet size to a smaller percentage can also help mitigate risks and protect your bankroll over time.