1. Device for rotationally driving the work rolls of a planetary mill for long rolling stock in which the rolls comprise a groove rolling the angles of the rolling stock and are mounted so as to rotate freely about their respective axes, which are parallel to each other and distributed on the periphery of rotors whose axis of rotation is itself parallel to those of the rolls, and consists of a ramp associated with each rotor and which is disposed on the outside of the latter and on which each roll runs before rolling the rolling stock, characterized in that : - any point on the rolling track (8) of the ramp (7) is located at a distance (Rr ) from the axis (2) of the rotor of between the distances to the said axis (2) from the bottom (13) of the groove of the roll (5) and from the point of contact (14) between the roll and the rolling stock to be rolled (6) which is furthest away from the axis (4) of the roll ; - and in that each roll comprises a bearing surface (11) provided at at least one end of the said roll and whose lateral surface constitutes a strip (9) by means of which the roll comes into contact with the rolling track (8) of the ramp (7).