There is a scheduled job (which you can access as an admin under 'System Scheduler -> Scheduled Jobs') named 'Stock Rule Runner'.   This scheduled job controls the logic for creating the task.   As it's defined, it creates the task in the generic 'task' table and assigns it to the stockroom manager.   The only left nav module where this would appear to the stockroom manager is the 'My Work' module under the 'Service Desk' application and they'll need the 'itil' role to see that module.   You could also create a separate module linking to the 'task' table if needed.