grant a privilege for roles (for example editors) and higher

My wordpress theme has a custom post-type. Only editors (and higher) should be allowed to use this post type.

I did this with:

function add_capability($role,$cap) {
    $role_obj = get_role($role); // get the the role object
    $role_obj -> add_cap($cap); // add $cap capability to this role object
}

function set_cpt() {
    add_capability('editor', 'edit_cpt');
    add_capability('editor', 'read_cpt');
    add_capability('editor', 'delete_cpt');
    add_capability('editor', 'edit_cpt');
    add_capability('editor', 'edit_cpt');
    add_capability('editor', 'publish_cpt');
    add_capability('editor', 'read_cpt');
}
add_action('init', 'set_cpt');

(I think) in WordPress 3.1 this was enough – all editors and higher had the right to use the post-type.

Now, in WordPress 3.2 only editors have the right to use the post-type.

Is there a way to grant privileges to role X and higher or would I have to mention every role?

Thank you!

[edit]

actually I found out that this never worked before. But is there another way to do it?

If you use the Members plugin, you can set it up like you want. It also has the possibility to add custom roles (your edit_cpt and so on)

also a lot of plugins also work that way:

<?php if ( current_user_can('manage_options') ) { do_something(); } ?>