The house average or house edge is the casino "tax". It should come as no suprise that the casino takes a portion of the money that you wager to run its business. The rest goes into a pool to pay the winnings. This is standard for any casino game, but in the case of roulette, it is important to realise that the house edge differs for the 2 main variants of the game: American Roulette and European Roulette.
European Roulette has 36 numbers and one zero pocket (37 in total).
American Roulette, on the other hand, has 36 numbers and 2 zero pockets: 0 and 00.
Now let's consider the house edge. The lower the house edge, the better for the player, as there is more money kept in the pot to pay winnings.
In European Roulette, the house edge is 2.7%. In American it is 5.3%.
So if there is one thing that you should take away from this article, it's that you should favour European Roulette over American.
The one casino online that adds an interesting twist to this is Betfair Roulette. Betfair are famous for their sports betting exhange of course, but they also run an online casino (see the full review at onlinecasinoking.com). And because they like to do things a little differently, they have removed the 0 on their virtual roulette wheel- giving a ZERO house edge game. There are some betting limit restrictions that go with this (in the self styled "zero lounge"), but nevertheless, this is an intereesting spin on the game and well worth a try.