The real trick to roulette is to get lucky, then quit while you're ahead. Every spin has a 1 in 37 (for European) or 1 in 38 (for American) chance of landing in a given pocket.
While mathematics can help you understand the odds and probabilities of different outcomes in a roulette game, there is no guaranteed way to win using mathematics alone.
Say a single-number bet has a 35:1 payout, and you betR$1. If you win, you'll get your money back plusR$35. Another example: If you win aR$100 bet (for a 35:1 payout), you get a total of $3,600 ($3,500 profit plus theR$100 you initially bet).