Users, roles, security levels and identity providers

In the identity provider, an expression can be used that gives a role permission to access a security level, like this:

containsAny( {idp-attributes:roles}, 'role_operators' )

Is it also possible to give a user access to a security level without using roles?
You can of course give a 'personal' role to a user and then use the same expression with the correct role name, but I would like to know if you can also do something directly with the username.