I found myself about 3 years ago looking into Roulette systems and strategies etc.. and It was based upon something similar to this. Basically what you did was record whether the no. each spin was H, L or M. As soon as there has been 5 spins where either H, L, M comes out you begin to play on that. I used $200 and lost it all using this exact system.
I've just done a search on google and have found the system im talking about. Interestingly enough it uses the same pictures as the website posted by zg, and infact it has the same content exactly. I'm presuming they're the same persons sites
http://www.andruchi.com/
In my experience, this system DOES NOT work.