Abstract: The roll assembly of a calender has at least one roll with a deformable shell which surrounds a rigid carrier and whose end portions surround discrete antifriction bearings. The intermediate portion of the shell surrounds one or more rows of hydrostatic supporting elements which can be acted upon by adjustable fluid-operated motors to change the shape of the intermediate portion in a plane including the axes of the one roll and the neighboring roll as well as at right angles to such plane. Stresses which are applied to the bearings for the end portions of the shell are monitored by several sensors which transmit signals to a control system to regulate the deformation of the shell in such a way that the stresses upon the bearings are minimized or reduced to zero. This enables the intermediate portion of the shell to undergo deformation which is best suited for optimum treatment of the material passing through the nip of the one roll and the neighboring roll.