The payout for a straight-up bet in roulette, where a player wagers on a single number, is 35 to 1. This means that if the ball lands on the chosen number, the player receives 35 times their original bet in winnings, plus the return of their initial wager. This high payout reflects the lower probability of winning on a single number, making straight-up bets one of the highest-risk options in roulette.