On the struts mailing list I received some info:
" .... -I believe that role to group mappings are app server specific, for example in weblogic you can associate a role with a user, list of users and/or group or list of groups in the weblogic.xml config file. From the weblogic console you can specify that a group contains one or more users and/or one or more sub groups. You should be able to do something similar with JBoss (??) ..."
Is this correct? Is this a JBoss-specific issue?