Abstract: A roll forming apparatus for curling a sheet of metal into a curved configuration having a plurality of sheet contours which apparatus automatically and sequentially varies the degree of curvature of a sheet of metal being treated by the apparatus as the sheet progresses through the apparatus. The apparatus includes a pair of pinch rolls and a bending roll for curving the sheet into predetermined arcs dependent upon the relative positions of the bending and pinch rolls, and a control mechanism to alter the relative positions of the bending and pinch rolls for each of a successive plurality of segments of the sheet as it travels through the apparatus. The control mechanism includes means to sense the actual distance the sheet has progressed through the roll forming apparatus and to compare the actual distance with one or more pre-established distances of sheet travel at which the radius of curvature of the sheet is to be changed.