Op have you ever used a VPN to access the site? Most times issues like this can arise when you use vpn especially free VPNs.

If you’re sure you don’t have any other account in rollbit then you should consider create a complaint at Casinoguru that way they’ll be able to provide proofs that you’re indeed multi-accounting in their site, right now I don’t see them coming to display such information in public for everyone to see here but they can over there since it won’t displayed.