I just believe they look at the ROI and saw they lost too much on me and then came up with such excuse. I just want to warn others who might be in profit to take your money out, and only deposit money you wont cry about if they confiscate. Rollbit is not transparent, and they can always close your account without letting you know why.
I see your point there after all. Yeah casinos or any other business venture don't relish the idea of you having profit over them and you have shown such experience and dexterity to keep winning and that probably the reason they want to let you go. You can just move on since you made profit from them and all deposit you made were from your winnings you had from them.
The best part is that you were able to withdraw what profit you got before they decided to shut you out. It is a lesson to be wise not to leave huge money in casino wallet or exchange because you don't have total control of the funds there.