Well I went to their terms and read regarding the [Promotions and Bonuses] it seems very risky condition, I think you must read it carefully and understand if you did not violate the rules, but as they have said there.
[ 9.5. Rocketpot may amend, reclaim, refuse or cancel any promotion at any time at its own discretion ]
Actually, most casinos and businesses have a similar clause in their terms of service. Many of them even add a clause giving them the right to adjust or replace their terms at any time they want at their own discretion. Probably as a way to avoid lawsuits.
But resorting to this clause and applying it whenever a customer make a big profit and requests a withdrawal is unethical by all means and will definitely damage the companie's reputation.
OP, I suggest moving this topic to the
Scam Accusations board and provide as many evidence as you can.