So lets say you open up your blog to guest posters, and you create a user for them, and possibly even a custom role.

You will usually find one or more menu items that you don’t want to show to your guest posters. How do you hide them?

Just take a look at the url of those menu items, and then use that to build up your function like this:

/* Remove Tools admin menu item for everyone other than Administrator */
add_action( 'admin_init', 'remove_menu_pages_for_all_except_admin' );
function remove_menu_pages_for_all_except_admin() {
 
    global $user_ID;
 
    if ( !current_user_can('administrator') ) {
	    remove_menu_page('tools.php', 'tools.php');
    }
}

Here are some of menu page names for the most common menu items that come with WordPress:

remove_menu_page('edit.php'); // Posts
remove_menu_page('upload.php'); // Media
remove_menu_page('link-manager.php'); // Links
remove_menu_page('edit-comments.php'); // Comments
remove_menu_page('edit.php?post_type=page'); // Pages
remove_menu_page('plugins.php'); // Plugins
remove_menu_page('themes.php'); // Appearance
remove_menu_page('users.php'); // Users
remove_menu_page('tools.php'); // Tools
remove_menu_page('options-general.php'); // Settings

Here’s one other bonus tip for you. If you want to remove the ability of a role to see the list of posts by other users, use this code:

add_action( 'load-edit.php', 'posts_for_current_contributor' );
function posts_for_current_contributor() {
    global $user_ID;

    if ( current_user_can( 'contributor' ) ) {
       if ( ! isset( $_GET['author'] ) ) {
          wp_redirect( add_query_arg( 'author', $user_ID ) );
          exit;
       }
   }

}