Roles are Permission templates allowing Users a certain set of allowed permissions within Projects.
Any User can select a Project and hover over their name in the User Panel on the right side to see all Permissions granted to them on that Project.
Administrators can create new roles.
Go to Administration, then select Roles icon on the navigation bar. This will reveal an overview of current roles, and you can create a new role by clicking the "+ Add Role" button on the top left.
If you are an Administrator looking to manage roles and users on the account, go here.