A system for rolling up a flexible sheet may include a frame; a friction element mounted on the frame, the friction element having an endless friction outer surface with a sheet-engaging portion positioned to engage an end of the flexible sheet lying in a substantially horizontal position relative to the frame; and a drive connected to the friction element to move the endless friction outer surface such that the sheet-engaging portions thereof move upwardly to engage the end of the flexible sheet and lift up and roll the end of the flexible sheet over on itself to form a roll.