A high roller is someone who spends a lot of money, often on gambling. A SPENDER (7 letters) is someone who spends money, a GAMESTER (8 letters) is someone who gambles, a SEMI (4 letters) is a large truck, a VIP (3 letters) is a person of importance, a fatcat (6 letters) is a wealthy person, and a bigspender (10 letters) is someone who spends a lot of money. All of these terms can be used to describe a high roller.