A device for axially supporting a rotating roller (1) resting axially on a fixed frame, at each end, by a contact ball bearing (3). According to the invention, the contact ball bearing (3) is mounted on the end of a support piece (5) consisting of a cylindrical insert (51) extended, on the roller side, by an enlarged base piece (52), fitting inside a recess (6) and bearing, in the axial direction, against the end wall (62) of the recess (6), by an axial bearing (66) and, in the radial direction, against the side wall (61) of the recess (6), by a rolling bearing (65) centering the insert (51) about the axis of rotation (10), the assembly being held in position by a cap (7) closing the recess (6).