A probability distribution is a listing of all outcomes and their respective probabilities. Obviously one can only win or lose at Roulette, so there are only two outcomes to worry about here. How much would one win and how much would one lose in a single bet? Find the probability of each occurring.
As for expected value - you have the right formula, but the incorrect values. Think about how much you're losing when you lose.
The answer should be negative (or casinos wouldn't exist), but not -6.27.