The Martingale Strategy in roulette involves doubling your bet after every loss, so when you do win, you recover all previous losses plus win a profit equal to your original bet. For example, if you start by betting $25 on black and lose, you would then bet $50 on black in the next round. If you lose again, you bet $100, and so on, until you win. Once you win, you start back at your original bet amount.