Show/Hide custom menu items as based on Roles/Web.sitemap file

Question

I have a custom menu, which leverages the standard asp.net sitemap. It works well but some of my pages are dynamically generated by URL rewriter, so they don't sit in the sitemap XML file. At the moment I rolled a custom solution which shows/hides menu items via CSS class and a programmatic check of the role that the user is in. It works ok until I visit a dynamic page that doesn't exist in the sitemap file. I've tried the "roles" attribute in the sitemap file with security trimming but it isn't working because I have a custom menu.

Is there a way I could leverage the roles attribute in the sitemap file to show/hide menu items for my custom control below, even when some pages are not in the sitemap? My menu control is below...

<div class="menu">
<ul>
    <asp:Repeater ID="rpt" runat="server" DataSourceID="smdsMenuPrimary" 
        EnableViewState="False">
        <ItemTemplate>                
            <li class="<%#GetDisplayClass((SiteMapNode)Container.DataItem)%>"><a href='<%# ((SiteMapNode)Container.DataItem).Url %>'><%# ((SiteMapNode)Container.DataItem).Title %></a></li>                
        </ItemTemplate>
    </asp:Repeater>
</ul>