Re the "edge" Mr J (post 6), it's also well known that a disadvantageous run (ie 30 heads in a row) can kick in in a genuine 50/50 game like coin-tossing.ie there is NO edge but you still lose.It is your inability to finance a negative progression which will kill. It can also happen when you have a probability ADVANTAGE. For example, at Roulette the house decides to pay 40-1 on single numbers tonight as it's the casino's 40th anniversary. You have to nominate ONE number only and, unluckily for you it only comes 9 times in 370 spins (not enough at Level stakes), instead of the expected 10 times. You use a negative progression BUT hit the limit. Uh oh; no house edge and the LIMIT brings you undone. You might argue that 370 spins is not enough for the "advantage" to show up, which is true. a positive progression, however, might still make you a winner, if for example you got a two or more of YOUR number close together.
The Zero has the REAL function of wiping out all the non single-number bets each time it appears in roulette. Unfortunately in any normal evening's roulette, if the zero DOES NOT APPEAR the house will still win due to the IRREGULAR appearance of the other numbers/bets forcing gamblers TO THE LIMIT, if negatively progressing.
In the coin tossing above, if you were on Tails, the thirty heads would simply be 30 straight 1-unit losses if using a positive progression. If you were lucky enough to be on heads in a no-limit game, it would be billions in YOUR favour.
As you can see "house advantage" is not the problem but the LIMIT, being imposed

The Fan. If you played Roulette with a positive progression and got to the limit, you would probably be ahead. (unless you were unlucky). You should have a pre-set win target and if not there yet; keep playing until you either DO get there OR you lose the lot. Once at your goal (you will probably overshoot at first) either leave immediately or else play the "overshoot" until
you fall back to your goal (and leave) OR get further ahead and then play on until you either fall back to the first "overshoot"(then leave) OR win again and get still further ahead. Then play until you either fall back to your second "overshoot" (then leave) oR win again and go still,still further ahead etc etc. In other words you are climbing a ladder. Cheers.