Check users role on each page

I have the following Sitemap
<?xml version="1.0" encoding="utf-8" ?>
<siteMap xmlns="http://schemas.microsoft.com/AspNet/SiteMap-File-1.0" >
    <siteMapNode url="default.aspx" title="Home"  description="" roles="Administrators">
        <siteMapNode url="~/admin/default.aspx" title="HomeMenu"  description=""  roles="Administrators, Editors"/>
        <siteMapNode url="~/admin/AddItem.aspx" title="Add New Item"  description=""  roles="Administrators"/>
    </siteMapNode>
</siteMap>
A user needs to be logged in to access any of the pages in the above sitemap.
Is there an easy way to set up in each page a check if the user is in the par ...