The invention relates to a method and a device for controlling a roll gap when rolling a strip (1) in a rolling mill including at least two rolls (3a-b,4a-b), and at least two roll gap actuators (6,7) that independently control the size of the roll gap. The device is adapted to receive information on the amount of wedge shape (POSactOS,POSactDS) in the strip thickness profile across the strip width, and to control said actuators, based on said information on the amount of wedge shape in the strip thickness profile, such that the relative reduction of the strip on both sides of the rolling mill become essentially the same.