We'll create fresh WordPress site with Custom roles for author installed. You have 20 minutes to test the plugin after that site we'll be deleted.
This plugin allows you to set users with custom role as post, page or custom post type author.
In addition, this plugin allows you to set what default roles (even subscriber, contributor) shoud appear in author dropdown list.
Plugin developed with WP_DEBUG set true on WordPress 3.3.1 => No notices, warnings or errors