A roller device comprises: an attachment bolt; a roller mounted on the attachment bolt, wherein the roller is configured as a roller unit including at least one attachment bush, a bearing, and a roller; and a fastening system to releasably fasten the bush of the roller unit to the attachment bolt. The fastening system comprises a clip fastening system to mount the roller unit on the attachment bolt without using tools. The clip fastening system comprises a radially encircling groove in the inner surface of the attachment bush, a radially encircling groove in the surface of the attachment bolt, and a flexible securing ring.