A straightening machine includes a frame supporting housings in which each housing receives a roll shaft rotatable about its axis. At least one first assembly includes a first guide defining a first convex surface and a first corresponding guided element defining a first concave surface. The first surfaces contact each other at a first contact surface. At least one second assembly includes a second guide defining a second convex surface and a second corresponding guided element defining a second concave surface. The second surfaces contact each other at a second contact surface. A device for rotating at least one roll shaft housing carries out a rotation being guided by the assemblies about a virtual axis transverse to a roll shaft axis, to compensate bending due to straightening of a product.