A roller is provided includes a cylindrical shaft supported by a main assembly of an image forming apparatus or a detachable cartridge. The cylindrical shaft includes a separation region on a circumference of the cylindrical shaft, where a pair of end portions of the cylindrical shaft oppose each other or are in contact with each other with respect to a circumferential direction relative to the circumference of the cylindrical shaft, and wherein the separation region extends in an axial direction of the cylindrical shaft. In addition, a rotatable cylindrical member is mounted around an outer circumference of the cylindrical shaft and is rotatable about the cylindrical shaft while an inner peripheral surface of the rotatable cylindrical member is in contact with an outer peripheral surface of the cylindrical shaft in a region of the cylindrical shaft other than the separation region with respect to the circumferential direction.