it or made by means of pulverisation metallurgical methods finally the roll is coated with a hard and wear resistant coating 7 material layers 5 and 4 may also both be of the same material and they can be manufactured in one stage fig7 shows a solution in which ducts 9 for example a duct system bent from sheet metal on the inside of which is formed for example by casting a base material layer 5 of e g cast iron are formed on the inner surface of the outer shell layer 4 which is of a material having better thermal conductivity there may also be an insulating layer on the inner surface of the inner layer 5 table 1 shows some approximate material values of materials which can be used in the method relating to the invention by selecting the materials so that their thermal conductivity increases when moving from the inner shell layer to the outer shell layer a higher roll surface temperature is achieved with less energy which may lower the total costs incurred by the thermoroll the roll structure can moreover be lightened which results in cost savings especially in multi roll calenders such as optiload calenders fig8 shows a solution in which the entire shell body is formed of a metal powder alloy which is produced by means of hip treatment and in which alloy are formed heating medium ducts 3 a 3 b on two different radial levels in the shell material if necessary also on.