Thank you first of all for the help. I'm not sure who the maker of the sliding glass door is or who manufactured the part. I looked through a couple of books today and was unable to find a match. It's bigger than most stores carry.
Casey from SWISCO responded:
April 18, 2017
Hi, This looks similar to our 81-156, Tandem Patio Glass Door Roller, compare the dimensions to see if it's a match.