This achievement sounds harder than it actually is. Go to any Roulette table (Found above the left staircase upon entry to the Casino) and bet the small amount possible on each number, with the exception of any one number of your choice.
When you bet on just 1 number, the odds of it appearing are very high, hence the reward. For the game to register a winning bet, you have to win more than you are betting. So for example, if you place 1 chip on every number except from 38, you're reward is 38 and because you've bet 37, it counts as a win.
Since you've placed a chip on almost every number, the odds of winning are about 99%.