A dozen bet in roulette is a wager placed on one of three groups of twelve numbers on the betting layout. Players can choose to bet on the first dozen (1-12), the second dozen (13-24), or the third dozen (25-36). To make this bet, players place their chips in the designated area marked for the dozens. A dozen bet offers a payout of 2 to 1, allowing players to cover a significant portion of the numbers while still providing a decent potential return on their wager. This type of bet is popular among players looking to increase their chances of winning by betting on larger groups of numbers.