I'm not sure of the difference myself. However I just launched a website (see the thread below this one) which scans several vendors for availability, including Rogue:
Ironscanner Scraper - Home
The site also sends out email notifications when items come back in stock. You may find this function useful to bridge the gap you've found on Rogue's site (where some items have a Notify Me option and others don't). To sign up for email notifications you can log in with your Google account using the button in the top right. Hope this helps!