Roller, separation device, image reading apparatus, and recording apparatus

A roller configured for contacting a medium comprising:

• a shaft;
• and
• an elastic body portion that is provided on an outer peripheral surface of the shaft and configured for contacting the medium,
• the elastic body portion comprises:
• a plurality of first recessed portions which are provided on a first side of the roller in a shaft mounting direction at intervals in a circumferential direction of the roller and each have a first bottom portion, and
• a plurality of second recessed portions which are provided on a second side of the roller in the shaft mounting direction at intervals in the circumferential direction of the roller and each have a second bottom portion, and
• wherein each of the first recessed portions is positioned between the adjacent second recessed portions in the circumferential direction of the roller in a side view of the roller in the shaft mounting direction, and
• wherein the first bottom portion is closer to the second side of the roller in the shaft mounting direction than the second bottom portion.