I've tried to lift the door but it doesn't come up high enough to take decent picture. With cold weather here I didn't want to risk it by trying to get the door out, as this is the back entrance to the house. It seem that the adjustable screw is about 8 inches from the edge of the door, from what I could see, in the metal assembly in the bottom, in the place where I would normally see the roller wheel, there was one of those small rollers sticking out (probably the one that hasn't fall out yet). I wonder if there's enough room in the door frame to just install one of the regular roller assemblies with 1 inch wheels. Thank for the tip.
As the weather gets better I'll try investigate further.