User roles are available on webs hosted by web servers running SharePoint Team Services from Microsoft and FrontPage Server Extensions 2002 only.
Note If you don't see the Manage roles option, you are probably in a subweb that uses the user account and roles settings of a higher-level web site of the server or virtual server. To work with accounts and roles, either go to the top-level web site, or set up unique permissions for this subweb. See your network administrator or ISP for more information.