Hi Paolo,

The role has to be implemented in Kentico CMS if you want to use Display to roles property . You could implement Custom Security Handler class. In following article is described how to integrate external user authentication (this way, you can also copy roles to Kentico):
http://www.kentico.com/Docs/DevGuide/security_handler.htm

How to create a role is described here:
http://www.kentico.com/Docs/DevGuide/managing_roles.htm?zoom_highlightsub=role

and how to assign user to role here:
http://www.kentico.com/Docs/DevGuide/managing_user_roles.htm?zoom_highlightsub=role

To have roles and users synchronized you can create your own scheduled task as described here:
http://www.kentico.com/Docs/DevGuide/scheduling_a_custom_code.htm

Best regards,
Ivana Tomanickova