I thought of something like this at one time for soccer bets but never tried. Regarding the roulette, with only one zero, one system that used to work ok for me was tracking streaks, let's say 1st Dozen not hitting for 12 spins, in this case odds might be in your favor, so you can do a short martingale betting on 1st or if you want to be more cautious bet on 1st and 2nd for eg. If you win walk out or at least hold you initial money.