Definition of High-roller
A High-roller qualified player is a player who plays high stakes and High-roller tournaments. Not everyone will agree on the precise definition of limits, but here's a rough idea of how poker limits are categorized. If you play tournaments with €20 and under, you are playing micro-limits. If you play tournaments between $21 and 100, you play small limits. If you play tournaments between €101 and €600, you play medium limits. And if you play tournaments between €600 and €10,000, you're probably playing high stakes. Tournaments at $100,000 and above are often referred to as the nosebleed. In games of cash games, tables that will have €blinds to €5/€10 (€1,000 of buy-in) will often be referred to as the high stakes table. A High-roller is a player who plays these limits.
High-roller is also synonymous with a very good player
The higher the limit, the stronger the players are. At least, those who win. When we talk about player High-roller, we're also talking about a very strong player, among the world's elite poker players. Some tournaments are also referred to as High-roller-player tournaments. Again, no precise indication is given as to the accuracy of the term, but say tournaments with a higher buy-in in a series of tournaments will be called High-roller tournaments.