In roulette, are there any certain combinations where your chances of winning money isnt stacked against you?

If you are playing blackjack with one deck, how many possible combinations of 21 are there?

Essentially, as many examples of combinations of cards that you can make 21 in the blackjack game that you can think of, thanks.

In roulette, are there any certain combinations where your chances of winning money isnt stacked against you?

Essentially, how many combinations of cards are there so that you can make 21 in the blackjack game.