Cannot find anything about Provably Fair either and 90% of the rounds I checked out resulted in a loose, so I suggest not to play on there.
I personally don't understand why people would gamble online with bitcoin. You could get scammed and it's not as fun as going to Vegas
>Implying that Vegas isn't one big scam
I, personally, like to gamble from time to time at BitVegas. I know how everything works, I know my odds, it's provably fair and I trust the owner, because I have had alot of contact with him. I don't see the point of not doing it.