A crop harvesting header with a cutter bar and a draper assembly has a draper canvas driven by a drive roller with a cylindrical roller body having an outer surface surrounding an axis of rotation of the roller for engaging an inner drive surface of a canvas wrapped therearound. The roller has a plurality of ribs arranged on the outer surface of the roller body extending along a part of the body in an axial direction and angularly spaced around the outer surface. The ribs have a height less than 6 mm and a width less than 6 mm arranged such that the ribs do not engage into any recesses in the drive surface of the canvas.