I would also like to know if I can somehow hide my nickname in this game, I don't want to be sniped.
At a high level: the bankroll is the counter-party to players bets. So when people bet and win, they win from the bankroll. When they bet and lose, they lose to the bankroll.
Casinos will generally base the limits (i.e. max-profit) based on the size of the bankroll so they don't risk bankruptcy. So generally the bigger the bankroll, the bigger bets and betters the casino can safely handle.
So the idea of a crowd-funded bankroll is pretty simple. Let's say the bankroll of a site is 99 BTC, and you want to contribute 1 btc. The new size of the bankroll would be 100 BTC, of which you contributed 1 BTC. Thus you own 1% of the bankroll. So that's your stake. Now if the size of the bankroll changes due to people gambling, you keep the same stake. (i.e. you'll make 1% of the loss and profit). At any time you came divest your stake to get bitcoin back.
Anyway, that's the rough idea of how it works at a high level.
You are free to create and use multiple accounts. Balances and internal transfers between accounts are private information. However bets are public information and there's no way to hide this. But I don't see why you'd care if people snipe your bets, it's not like it changes your bet outcome or the game outcome