No matter how great your strategy, gambling will not be separated from luck. It's not that I'm not using a strategy in gambling, but I believe that luck is the main gamble. So my strategy is, I gamble within the limits of the money I have, and hope luck is always on my side.
Roulette is mostly the luck based game as strategy here does not work. You need to be luck to get the things right and come your way and this could happen even with out strategy if your luck is good you will win big and make money from it.
As long as it is gamble, everything is based on luck, be it roulette, dice, or whatever you can think of and no matter the strategy you think you can come up with at the end of it all, what matters the most is how lucky you get eventually.
Sure, I have heard cases in which strategies kind of helped some people when it comes to gambling but one thing they have not realized is that even with those strategies, they are just there most of the time to help you prolong the game and may be give you a winning chance, but it is not like it should be a guarantee that you will end up winning at all.