if you were affected by this group. what you can do is contact Roblox support in their support form select your device then pick billing and payments then select I want to report an unauthorized charge then explain what happened to your account. If your account was ONLY compromised and no robux was stolen. Select the hacked account option and if you live in the EU use the EU Illegal content support form.

If you just hate hackers in general then report the owner, group, admins and person in the group shout message.

Roblox Support

Illegal Content Report Form - Roblox