If you find yourself in the situation of having too many users on your Discord Server, don't worry. There are a lot of bots out there which can help you with giving roles, but the most used one is probably MEE6. This one works through a plugin. There are some bots out there which do not require a plugin. For example, you can try Reaction Roles Bot. These require a little bit of setup which can be done through commands, but they offer pretty straight-forward instructions.