What are the use of roles?

Answer 1

To simplify user management. By creating a role, you can grant a number of database permissions to it, then grant the role to users. This saves you having to manually grant a myriad of different permissions individually to a number of users.

Answer 2

my role at my company is finusr. So everyone belonging to that role, is permitted to do certain things. I don't have access to everything. only read permission to certain tables. Some people have more access to certain tables so they are assigned a different role.