A roller assembly including: a frame； a first undercarriage connected to the frame, the first undercarriage comprising: a first body； a rear roller connected to the first body； and a first overlapping roller that is elongate and connected to the first body； and a second undercarriage connected to the frame, the second undercarriage comprising: a second body； a front roller connected to the second body； and a second overlapping roller that is elongate and connected to the second body, wherein the first undercarriage is positioned adjacent to the second undercarriage such that the first overlapping roller overlaps the second overlapping roller.
