Filtered signal values are extracted from an input signal. These segments are spread into the lateral regions of the material to be rolled into a flattened profile which is as an object for at least one-staged strip rolling so that the spread ratios between the diameter of the rod and the width of the strip of greater than 2,8:1 are achieved. A digital signal processor is associated with each camera. The concrete is poured within the area defined by the form to a height determined by an upper edge of the form so that the temporary extended border portion of the slab is supported on the recessed top wall.