Define new user capability for custom post types?

If I create a custom post type and want to create custom capabilities for that, how do I do this? For example, I want to let my Editors to edit and create and delete posts and pages, but not the custom post type I’ve created? I also want to have the possibility to change the capabilities later with this plugin: http://wordpress.org/extend/plugins/user-role-editor/ (see the screens of the available capabilities: http://wordpress.org/extend/plugins/user-role-editor/screenshots/)
I’ve done this by now this way:

global $wp_roles;

if(!isset($wp_roles)) {
    $wp_roles = new WP_Roles();
}

// add capability $cap to role $role
$roles = $wp_roles->get_names();
$wp_roles->add_cap('administrator', 'organize_matches');

But then even I as administrator am not able to save the custom post type (and yeah, I mentioned ‘organize_matches’ in the ‘capabilities’ argument when registering the custom post type). Really appreciate Your help!