Wagering will always be a discussion point when it comes to casinos.

@badjacks - that is why most casinos do not allow bonus wagering on roulette.
Red/black same time betting is generally regarded as outside the scope of normal play.

@mem - thanks for weighing in here.
The basics of wagering versus deposit still get confused by many players.
Your example explains this clearly but I would like to bring up a different game.
Slots
The house still has an edge but there is the chance for jackpot.
As a slots player the bonus extends your play on the machine.
The house edge remains the same but your chance to hit a jackpot increases.
This is obviously a different example to single payout games like blackjack and a different player as well.

There are 2 important questions here:

1- what games do you like playing?
As mentioned its a very different situation with roulette and with slots.

2 - what is your objective in taking the bonus?
If your aim is to meet the absolute minimum of wagering requirements and be able to withdraw a marginal profit, thats mostly been discussed above.
Or if you view the bonus as giving you more play for less buyin and you want to win money by actually playing the games.