Can someone explain intelligibly how the Bankroll works?
The bankroll is the pool of money that the house uses to pay out winners that bet on the bustabit multiplier. The max profit that players can win from a round of the game is determined by the size of the bankroll. The larger the bankroll, the more players can win. Each player can only win 1% of the bankroll in a single round. Similarly, all players combined can only win 1.5% of the bankroll in a single round. Players can bet on the house (i.e. become bankrollers), and their bet is added to the bankroll such that they win when the house wins and they lose when the house loses.
If you decide to invest, be aware that there is a 2% dilution fee per investment, meaning 2% of you bankroll investment will instantly be distributed amongst all bankroll investors who joined before you. To quote bustabit's language again, the 2% dilution fee is bustabit's " way of rewarding long-time bankrollers. It's never too late to become one!"
For what period is interest accrue?
You will earn (or lose) for as long as you have money invested in the bankroll. Your investment will fluctuate after every completed round, with your bankroll balance updating in real-time. If a player loses a large sum of money, your invest will earn proportionately. However, if a player wins a large sum of money, your invest will lose proportionately.
How to cash out?
Investing/Divesting is very easy. Simply go to "Bankroll" -> "Change Investment". From there you just select the amount of bits you'd like to invest/divest. To invest, you'll need to deposit BTC to your bustabit account first.
Can I withdraw my money at any time?
Yes.