One rules in some casino.
Most of the casino have "wagering requirement" before you're can withdraw the money, like 1X from the money you're deposit. I read the story you're deposit 12,800$ and only wagering 1000 USD?
This is also what I am thinking, it is possible that Rollbit is implementing a wagering requirement before anyone can withdraw what they deposited to prevent players to use the platform for money laundering.
Your fund getting flagged with "money laundering" system, that's why the withdraw is not automatically process and need their manual process. Contact them, 4 years in gamble is always the one who got problem is from "sportbet" user due they are activity like this.
It makes sense since @OP only wagered $1k out of $12k he deposited. With the huge amount of money being deposit and the ratio of amount being wagered before withdrawing, it will really alarm the system of money laundering. The platform may also ask @OP the source of the fund if they suspect that the money came from illegal means. We have seen this kind of incident where a casino asked for the source of the fund so it is not impossible for Rollbit to ask the same before releasing or confiscating your fund.
So to update. They let me withdraw in the end so I have my funds back.
Good to hear that you got your fund back and did not undergo such long process of source of fund verification

But they asked a lot of weird questions on the KYC video call. Even asked to log into my wallet whilst on live share screen?
I think it is better than you providing the source of funds which may take longer than what they asked you to do on the live share screen.
Btw, you should edit your title since the case is already resolved, it will be unfair for Rollbit if you keep your title this way.