A roller bearing unit for rail vehicles, having an inner bearing ring, an outer bearing ring, rolling elements arranged between the bearing rings, and at least one retainer element. The inner bearing ring and the retainer element are configured to be arranged on an axle. The retainer element is arranged radially between an axial end of the inner bearing ring and the axle, and radially between a contact part lying against the end face of the inner bearing ring, and the axle. The retainer element has at least one sealing element sealing the inner bearing ring.