That guy is caught for suspicious depositing behavior. I don't know, maybe his funds came from an illegal source, maybe Roobet asked him to provide his earning source-related documents.
Only Roobet team will be able to give a good explanation about this, wait, and see how they handle this issue.
One more doubt is that do you close the account if the coins came from a mixer as per the image posted by the user it says that and i have not heard any situation where a gambling account is closed because they used mixers.
I think using mixing service is not belongs to severe-risked indicators. If their system is able to detect about it and think the funding source is suspicious then they've the rights for asking KYC and earning source, Accounts getting suspend only if the core team detect that the risk to be related to illegal activities.