To be able to manage roles the user should have the ‘Administrator’ role. Without this role the user won’t be able to see the roles (unless they have the permission to update user roles), update or delete roles.
Assigning a role to a user
You can assign roles to either existing users or when you create a new user. To do this navigate to the ‘Users’ screen and either find a user you would like to assign a role to or create a new user. Once pressed on the row of a user or on the ‘+ Add user` button the user modal opens. In the profile tab of this modal you can select the role for the user. If you press the edit button (the button with the pencil icon) the role dropdown should get enabled. If not it could be that you are missing the permissions to be able to update user roles. By opening the dropdown you’ll see a list of roles that this user can receive pick the role you would like to assign to it and then press the save button (the button with the save icon). The user should now have the selected role assigned to it.