How to add the admin role to Drupal 7 after upgrading from Drupal 6?
You can set an admin role in admin/config/people/accounts or by going to Configuration -> Account Settings under "People" label.

The help text under the select box says:


  This role will be automatically assigned new permissions whenever a module is enabled. Changing this setting will not affect existing permissions.


So remember to assign the existing permissions to this new role! But whenever a module is enabled and new permissions are created, this role will automatically be granted those.

To create new roles you go to People -> Permissions (tab) -> Roles (secondary tab)