It does work in most cases. To try it out, use a pack of playing cards. Remove the top 4 cards from each suite of the pack to leave 36, and add the joker to represent the roulette wheel '0'. Shuffle and deal, and watch how your imaginary black and red bets go.
The problems are - house limit, as Squarebear says, and house rules, as mentioned on the web page.
If the house limit prevents you from placing your next bet, and you start again from scratch, you'll spend a very long time in trying to recoup your loss.