I'm not sure what could be the bankroll or how much is your bet to be called as a high roller, for me my bank roll is around $500-$800 per deposit and my bet is around $50-150 per match (Sports betting) some people may think this is average but some people think this is high we have different perspective.
Yes, that's right but for me, if a person or gambler has deposited more than $500 and made a bet of at least around $70-$100, I guess that's already part of the high roller. If we look up I don't think there will be a limit and therefore every gambling site has at least a limit on the amount of the bet applied. So, with the amount of money that is said to be in the $50-$500 range already high, it is clear that those who can bet higher than that value are high roller gamblers, because not all gamblers can consistently bet at $50 and above, therefore when they can be consistent betting $50 and above I think is part of the high roller.
It would be interesting to know the opinion (statistics) of bookmakers on this matter. I think that the top 10 percent of all players are considered high rollers automatically, so their average bet could be a guideline in order to accurately understand the level at which a player becomes a high roller.