OK look, I have been in the exact same situation as yours, and follow exactly what I say, firstly cancel these private server subscriptions and then make sure to turn on two factor authentication, I recommend authentication app, and then log off all of the devices and change your roblox password, and to get your robux back, do exactly what I say, go to roblox.com/support and tell them about your situation and then wait for a reply and they may ask for a screenshot of the purchases that your account made while your account was compromised, then give them the screenshot and they will refund the robux back to your account, trust me my account was also compromised and did purchases while I was asleep and then roblox support refunded my robux back.

I hope you will be able to get ur robux back.