Rollbit has great reward system indeed but I think their referral system is really bad (at least on the lowest level).
I invited my friend to play, he wagered $165 000 and I got only like $170 commission, when on most other sites that would've been at least 350-400+
I asked about this with support and you get 10% of the house edge of the wagered amount from the referred user. The calculation sounds about right if your friend wager on a 1% house edge game but I doubt that anyone would wager $165k solely on 1% HE dice games but yeah I guess they decreased it due to all those bonuses they gave