Replacing rollers on my American craftsman patio door

Your door may have originally had a sill cover which has since been removed. As for the rear stationary door retainers, you might just have screws on the inside rear edge of the frame pocket locking in the stationary door. 

All that being said, without you removing both doors from the outside of the house, raise up the rollers you now have in your sliding door then see if you can lift off the sliding door from the inside of the house.