Web.sitemap roles not works

Web.sitemap:
<?xml version="1.0" encoding="utf-8" ?>
<siteMap>
  <siteMapNode title="test" description="test" roles="Admin"
    url="default.aspx">
    <!-- other <siteMapNode> elements -->
  </siteMapNode>
</siteMap>


Web.config:

<!-- .other configuration settings -->
    <siteMap defaultProvider="XmlSiteMapProvider" enabled="true">
      <providers>
        <add name="XmlSiteMapProvider"
          description="Default SiteMap provider."
          type="System.Web.XmlSiteMapProvider "
     &nb ...