In paper and board machines the position of a rolling device relative to another rolling device and/or the force exerted by the rolling device on the other rolling device or any variable acting on these is measured, and the value of the measured variable is compared with the set value of said variable in order to obtain the difference value of the variable, and the position of the rolling device and/or the force it exerts on the other rolling device is controlled on the basis of the difference value. The fluid pressure of the hydraulic means (5) and/or the flow velocity of the fluid to the hydraulic means is changed in order to alter the difference value of the variable by opening and/or closing at least one digital valve in a digital valve pack (7) functionally connected to the hydraulic means (S).