Hi Kurt,
It's not possible for user with 'None' privilege level to access to Admin interface. You can read more about privilege levels in documentation.
Regarding about role issue that you reported, how many roles specific user have assigned? If user have more then one role, you will gave access as UNION of all allowed permissions for both roles. You can check roles assigned to user by going in 'Users application -> (Edit specific user) -> Roles tab'.
Best regards,
Dragoljub