High rollers are given regular free spins, free bets and cashback on losses except that they have higher limits on these. A casino may be giving 200 free spins to regular players and 800 spins to high rollers. They get these other perks too:
Free casino branded goodies like hoodies, shirts, caps, mugs.
Priority customer care support.
Cashback on losses.
Early access to new games and casino features.
Tickets to invite-only tournaments, events and parties.