Problem with Custom RoleProvider Class

Dear friends,
I have written my custom RoleProvider class and custom MembershipProvider class in my application in order to get the information from my existing database.
The User validation is working fine with Custom MembershipProvider Class, but the Custom RoleProvider Class is not working.
Please help me out.
Web.config section:
<system.web>
        <siteMap defaultProvider="AspNetXmlSiteMapProvider" enabled="true">
            <providers>
                <clear/>
                <add name="AspNetXmlSiteMapProvider" type="System.Web.XmlSiteMapProvider, System.Web, Version=2.0.3600.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a" siteMapFile="web.site ...