Hello,
These windows are aluminum, double pane and are approximately 30"x50". The roller is in a nylon carrier that is about 11/16" wide and 1 3/16 long with a screw hole at each end. The roller itself is flat brass and 3/8" wide with a diameter of about 1/2". See picture. The windows have a single roller at each end and are installed vertically. Double rollers wouldn't hurt and there is plenty of room to install them with the correct carrier. Depth of window frame is about 3/4".
Thanks for any suggestions you can give.
David