Even you will sue the ETH, BTC, or LTC, the withdrawal fee was still the same, it is I think ranging from 6-8$ while BTC is on $10 which is still good enough.
How is $6 - $10 good enough? It is unacceptable in my opinion. Some crypto gambling sites charge zero withdrawal fees while some others provide various options(Slow, Fast etc) to bring the fees below $5. Roobet needs to improve in this aspect.
Whales might not mind these fees, but they are part of the minority. The majority of gamblers are small-scale gamblers who have issues with high withdrawal fees.