Can I hide/show asp:Menu items based on role?

You can remove unwanted menu items in Page_Load, like this:

    protected void Page_Load(object sender, EventArgs e)
    {
        if (!Roles.IsUserInRole("Admin"))
        {
            MenuItemCollection menuItems = mTopMenu.Items;
            MenuItem adminItem = new MenuItem();
            foreach (MenuItem menuItem in menuItems)
            {
                if (menuItem.Text == "Roles")
                    adminItem = menuItem;
            }
            menuItems.Remove(adminItem);
        }
    }

I’m sure there’s a neater way to find the right item to remove, but this one works. You could also add all the wanted menu items in a Page_Load method, instead of adding them in the markup.