The roulette probability of correctly predicting the winning number in the European variant is 1-in-37, or about 2.70%. If you play for 30 rounds, you have a 55% chance of getting the number right at least once.
Games like Blackjack, Craps, Baccarat, and Roulette give you the best odds of winning. The Wheel of Fortune and Keno give you the worst odds of winning. Table games always have better odds than slot machines.