The heated roller of a heating device for warming a film strip comprising thermoplastic plastic is embodied to be manufactured less expensively, including its coating, even with a relatively large diameter. Moreover, it is lighter and can be brought to a more uniform temperature. This is accomplished in that the heated roller comprises a plurality individual segments that can be produced, including all holes, webs and grooves, from an aluminum alloy in an extrusion-molding process. A special clamping strip connects adjacent individual segments together to form the roller.