The invention relates to a rolling bearing assembly device having an inner race, an outer race, at least one row of rolling elements disposed between the inner race and the outer race, and a sleeve mounted in the bore of the inner race. The sleeve provides a radial bearing flange, the lower edge of which has a portion that is inclined towards the interior of the device, the inclined portion in contact with a locking washer. The sleeve also provides at least one slot extending axially towards the inner race from the lower edge of the radial bearing flange, the lower edge being disposed on the opposite side from the inner race.