If you want to remove the door, slide a flat blade under the door and lift to remove to free the roller of weight. With the help of another screwdriver adjust the screw. Now the door will slide easily.
I would lift door straight up. Then have somebody get down on there knees and see if they can lift those wheels up with a screwdriver or something. The wheels should be spring loaded. If you get one up then pull the bottom out and work on the other. May work or may not.
That is true for most rolling screens, but not the actual operating panel of the door (regarding springs). The wheels of the operating panel are mechanically adjusted.
Replacement Windows, doors, siding, roofing, insulation, and BPI certified energy consulting, Building Analyst 5051322 www.HomeSealed.com