A fact well known about roulette is that in each spin the probability of winning a single bet is always the same. The probability of winning in a roulette spin can be computed by dividing the numbers in your bet by 37 (European) or 38 (American).
For example: One bet to a line (6 numbers) the probability is obtained as follows:
6/37=0.1621 which in percentage is 16.21% for the European roulette case. For American 6/38=15.78%. Results for all kind of bets can be seen in next table:
When is the best time to bet?
It is also possible to compute the winning probability of multiple spins by generalizing the winning probability formula of a single bet.
Let say that in European roulette the probability of NO black colors in 6 roulette consecutive games is (19/37)^6=0.018. It means that we have a probability of 1.8% to obtain only red numbers or zero in 6 consecutive roulette games.
A more interesting result can be obtained by the opposite result (at least 1 black color in 6 roulette games). The occurrence of black color probability is 1-0.018 =0.9816.
This means that it can be expected, with 98.1% of probability that at least one black color will appeared in 6 roulette consecutive games. And this is known as the theoretical delay of a bet.
The next table shows the theoretical delay of a kind of single bets:
The problem with the theoretical delay is that it is THEORETICAL!!!
In real life the delay can be greater than the value computed. When that happens it is known as the gambler’s fallacy that says:
If something happens more frequently than normal during some period, it will happen less frequently in the future, or that, if something happens less frequently than normal during some period, it will happen more frequently in the future (presumably as a means of balancing nature).
In conclusion, theoretically, it could be possible to improve your bet by waiting the delay of your bet. However, you should BE CAREFUL because at least one time each 100 roulette games the real delay exceeds the computed probabilities!!!