A roller input device includes a casing and a roller. A roller seat and an encoder are disposed in the casing. The roller is pivotally disposed on the roller seat. The body of the roller includes a shaft portion, a first side, and a second side. The first side and the second side are at opposite sides of the body. The first shaft and the second shaft of the roller are connected to the shaft portion and respectively extend from the first side and the second side. An end portion of the first shaft and an end portion of the second shaft away from the shaft portion respectively have a first connection portion and a second connection portion. A structural strength of the first connection portion is greater than a structural strength of the second connection portion, and the first connection portion is connected to the encoder.