Roller unit for laying cables in a plant for laying cables and plant for laying cables comprising the roller unit

Roller unit for laying cables (11, 12, 13), comprising a frame (23, 23′) where at least one pair of sliders (25, 25′) are positioned aligned parallel to a laying direction (S1, S2) of the cables (11, 12, 13) and each provided with at least one pair of wheels (28, 28a, 28b) supporting a cable (11, 12, 13) to be laid; said sliders (25, 25′) are hinged to said frame (23, 23′) and rotatable around respective axes of rotation (A, A′) so as to vary the inclination thereof with respect to said frame (23, 23′) and therefore to vary the radius of curvature of the cable (11, 12, 13) supported; said wheels (28, 28a, 28b) are provided with an annular groove (32) to support the cables, delimited by containing wings (33) and able to define a contact and sliding surface of at least one of said cables (11, 12, 13), wherein at least said annular support groove (32) is made of or covered by a technoplastic material with polyamide (PA) base reinforced with glass fiber, if the supported cable is a conductor (11, 13), or by means of a metal material of great hardness, in particular pearlitic-ferritic lamellar cast iron GJL250, if the supported cable is a towing cable (12).