Hello, Lisa. There could be a few reasons why your door is having trouble rolling. Before you buy anything, I recommend cleaning and lubricating your track (you can use a wax stick like our 75-077 to do this). If you're lucky then the only thing holding your door up was some dirt and debris, which is an easy fix.
While you're down there, check the track for any signs of obvious damage. Look for any dents, dips, or even cracks that could be hanging up operation.
If your door still has trouble opening after that, then odds are the rollers need to be replaced. We can see if any of our parts will work, but I need to see photos of your original roller to be sure of my recommendation. In the meantime, you can see if our 84-074 is a match. This is no guarantee but it is commonly purchased with the 84-223.
Otherwise, the only way to know what roller your door needs is to use the original as a reference. Please let me know if that would be possible.
