the roll region surrounded by the web material the web material is identified in fig3 with reference numeral 22 in all the above described construcstions the displacement member 4 is supported inside the roll jacket in a radial direction in a known manner by welded axially extending fins such a fin is shown in fig3 and identified with reference numeral 23 in the construction shown in fig4 the roller jacket 1 the flange 2 the pins 3 and the displacement body 4 substantially correspond to the respective parts of the previously described constructions the heat insulation of the end regions of the roll relative to the drum shaped flow chamber 6 is carried out here similarly to the construction in fig3 here also the dead chamber 20 filled with the fluid is provided which is locked from the flow chamber by the ring 21 in this construction as well as in the construction of fig3 the chamber 20 can be filled with another material for example with a loose insulating material which further reduces the heat transfer in contrast to the above described constructions in the roll in accordance with the construction of fig4 the flow passage 9 is thermally insulated from the pin 3 by an air gap 30 the air gap 30 need not extend over the entire length of the pin it suffices that the regions of the pin 3 which are close to the flange be insulated by such an air gap the end wall of the flange 2 which faces toward the flow.