Abstract: A roller contact bearing unit, in particular for the hub of a vehicle wheel, including a radially outer rotating race (10), a radially inner stationary race (11), a sealing device (16) between the races (10, 11) and a device for measuring the rotation speed of the outer race (10). The measuring device includes an encoder wheel (13) in the form of a radially oriented annular disc made of plastic or rubber magnetized material, and an annular insert made of non-magnetic metal (14) which is suitably shaped to form: a constraining means (14a) for fixing the insert (14) onto the outer race of the bearing unit, an axial abutting means (14b) suitable for abutting against a lateral surface (10b) of the outer race (10), an annular seat (14c) for housing and externally enclosing the encoder wheel (13), and a support means (14d) for a rubber element (15) which forms a sealing covering (15b) suitable for sliding against a surface (16) which forms part of a non-rotating element (11) of the bearing unit.