The standard deviation for roulette outcomes is calculated by first determining the expected value of the game, which is based on the probabilities of different outcomes. Each outcome's deviation from the expected value is then squared, weighted by its probability, and these squared values are summed. Finally, the square root of this total gives the standard deviation. In essence, the standard deviation quantifies the variability of outcomes, reflecting how much the results of spins tend to differ from the expected outcome, allowing players and analysts to understand the level of risk and unpredictability involved in the game.