To delete a wordpress user role you need use this two lines:
$wp_roles = new WP_Roles();
$wp_roles->remove_role("your_role");
if you want to list the roles before delete one of them:
$wp_roles = new WP_Roles();
$names = $wp_roles->get_names();
print_r($names);
no plugins needed, 100% guaranted!
