I don't understand this part. What do you guys mean by "they don't give big wins"? 
I didn't understand this part as well to be honest. I have observed many people win big amounts from Roobet which is why what they stated doesn't really make any sense. The only difference, and that's a big one, actually, is that on some other sites you can have problems with withdrawing, while it's almost instantly on Roobet.
I have to disagree with you here. Instant withdrawals are available in many crypto gambling sites(Not just Roobet) though it depends on the amount that you are withdrawing. I like the fact that Roobet listened to the community and reduced the BTC withdrawal fees recently which is a big plus point. I just wish they would get rid of that KYC crap which would make it even more appealing overall.