I am looking for a door roller that seems to be a bit unique. The door frame has "Summit Window" as the manufacturer. The rollers themselves have no identifier. The housing of the roller assembly looks like your 'Reverse Mount Roller Assembly' (p/n 81-141), but the roller assembly within the housing would need to be flipped (not reverse mounted). The offset in the mounting flange (picture #3) allows this roller to sit slightly more recessed in the door than a standard tandem roller. With a standard tandem roller the mounting flange is in the same plane as the bottom of the housing. A standard tandem roller will not clear the outer lip of the window frame, even when fully retracted. Plus, the adjustment screw of a standard tandem roller will sit about 1/4" below the adjustment screw hole in the door frame because it is not recessed.
Mounting hole centers are approximately 5 3/4" apart, housing width approximately 3/4".