LDAP Authorization

Hi people, I am using XWiki with LDAP authentication, and its fine, but I can't figure out how to make the authorization process. Inside xwik.cfg I have a key (xwiki.authentication.ldap.fields_mapping) where I make the ldap mapping for xwiki, so I map xwiki "name" for my ldap return key and so one, what I need to know is what's the xwiki key that I have to map my ldap role field? Or I need to use something else to configure Roles? If someone has the link for the doc that explains it, please send me. Please if anyone don't understand my question, tell me, I will try to express myself better :-) Regards, Igor Regis