At least one of the rolls if formed of an axial support member, surrounding roll shell and a movable support element such as a piston. Both rolls are mounted at each end in a common support with each support made of upper and bottom blocks which are joined to each other by detachable connecting elements. These detaching elements allow the blocks and, thereby, one end of one roll to be raised or lowered to permit entry to the nip between the rolls. The connecting elements can also be prestressed to a degree higher than the maximum force which would occur between the rolls during use.