I had never played anything on rollbit before this time.
Unfortunately, there is nothing you can do to prove this. It's basically your word against their's.
The casino, on the other hand, could have given you a chance to prove you are not the same person as the one they suspect to be your alt by asking both of you to submit your documents and verify your identities. I don't know why they didn't do so before permanently banning your accounts!
Right now, I don't see how this case can be solved without resorting to mediation!
They just know who they are dealing with based on the information generated by their security system, so they do not bother to ask for documents although its necessary before banning the account, they seem confident that OP will fail in their KYC, and I agree that OP's only recourse is a third party mediation he can prove his innocence or prove that Rollbit all along.
OP here is a prolific sportsbook abuser, previously banned from our platform for circumventing sportsbook limits (creation of new accounts).