The rotating cylinder for processing a web material comprises an essentially rigid cylindrical core (13), on which is fitted an interchangeable sleeve (45) of elastically expandable material whose rigidity is less than that of the material of the core; the sleeve is axially and angularly fixable to the core and is provided on its outer surface with a relief pattern. For each end of the 3 cylinder, there is provided at least one corresponding mechanical locking member which can be fixed to the corresponding end of the core of the cylinder and which interacts with the corresponding end of the interchangeable sleeve to lock the interchangeable sleeve angularly with respect to the core of the cylinder.