Need to view a particular page of your JomSocial site in RSS?
Try adding ?&format=feed to the end of that particular page's URL.
For example,
Recent activites rss feed:
http://[yourjomsocialsite.com]/index.php?option=com_community&view=frontpage?&format=feed
User's rss feed:
http://[yourjomsocialsite.com]/index.php?option=com_community&view=profile&userid=<USERID>?&format=feed
Viewing all photos:
http://[yourjomsocialsite.com]/index.php?option=com_community&view=photos&task=display?&format=feed