Many casinos allow to withdraw with the same currency you use to deposit. I guess they have these rules to avoid money laundering or abuse to use casino as mixing tool for money flow from fraudulent activities.
Roobet has this rule in ToS too
Roobet offers mainly a chat and gambling Services, Roobet does not offer any currency exchange Services, you may only withdraw in the same currency as You deposited.
That's very obvious, what I believe! Their main purpose offering best possible gambling experience nor to provide exchange services. Some casinos are offering exchange service though, as competition is so high. But, Roobet should maintain on their TOS as they were promised to serve.
I tried to request a withdrawal and I discovered that there's an option to select the processing fee with Low, Medium and Priority, theses past few weeks the fee has been really crazy and I think this is a very welcomed development. However, I'll be more interested in a feature whereby we can chose to withdraw in either Ethereum or Bitcoin, since the payment are converted automatically to USD after deposit, I think it will be better if we can withdraw in either currency regardless of the means of deposit.
I guess, withdrawal thing become now more easy to use. That is an issue with the withdrawal expenses, when charges were relatively so high for min withdrawal. At last, On withdrawal they actualize Low, Medium and High things, which is pretty impressive.