Logically you wont be able to withdraw $1000 even if you win those 4 freerolls as the 1st winner because the amount is a prizepool which is divided for several winners. If you win some $$ then you will be able to withdraw as the winning amount is yours.
Okay, makes sense that the bonus is not to be withdrawn. However, If one wins, say, $100 and still has $700 from the initial bonus then how will it be decided whether it's his money to be withdrawn? Can different kinds of money be divided into separate categories for that?
I don't believe there's $1k bonus anyway. It's just too crazy and it makes no sense to give so much money (even though it still stays on your website) for people to try playing in the casino. And why is it nitrogen rolls whereas the casino is btcjack? Does nitrogensports even know about it? I don't know where's the set up here but that looks really suspicious to me.