<!--appSettings вставил я-->
  <appSettings>
    <add key="EnableSimpleMembership" value="false" />
  </appSettings>
  <system.web>
    <compilation debug="true" targetFramework="4.0" />
    <authentication mode="Windows"/>
    <identity impersonate="false" />
    <roleManager enabled="true" defaultProvider="WindowsProvider">
      <providers>
        <clear />
        <add name="WindowsProvider" type="System.Web.Security.WindowsTokenRoleProvider" />
      </providers>
    </roleManager>
  </system.web>

if(User.IsInRole(@"RSZM\Users"))
  Label6.Text = " <div>Is an administrator or sales person</div>";