Custom User Roles not displayed in Author List Box

Hi,

It seems that Custom User Roles with capability of level_1 are not displayed in the author list box!

function staffBravo_user_roles() {
   add_role( 'staff', 'Staff', array( 'read' => true, 'level_1' => true ) );
   add_role( 'department-manager', 'Department Manager', array( 'read' => true, 'level_0' => true ) );
   add_role( 'outlet-manager', 'Outlet Manager', array( 'read' => true, 'level_0' => true ) );
   add_role( 'company-manager', 'Company Manager', array( 'read' => true, 'level_0' => true ) );
   remove_role( 'subscriber' );
   remove_role( 'contributor' );
   remove_role( 'author' );
   remove_role( 'editor' );
}
register_activation_hook( __FILE__, 'staffBravo_user_roles' );

Do you have any idea? :/