The invention relates to a roller (10′) for a roller conveyor, having an outer cylinder (12′) that is rotatably mounted on a stationary shaft (14′) and which may be driven by a motor (16), the roller (10′) having an optoelectronic sensor system (20′) comprising a light transmitter (22′) and a light receiver (24′). The optoelectronic sensor system (20′) is positioned relative to the outer cylinder (12′) in such a way that a light beam (22a′) emitted by the light transmitter (22′) extends along the exterior of the outer cylinder (12′), essentially parallel to a surface line of the outer cylinder (12′), and the light transmitter (22) is provided inside the outer cylinder (12′), and optical deflection means are provided for guiding the light beam (22a′), emitted by the light transmitter (22′), to the exterior of the outer cylinder (12′).