The disclosed conveyor-belt cleaning assembly includes a ribbed cleaning roller that is restrained by a blocking device against moving closer to the belt than an operating position at which the ribs of the cleaning roller sweep at high speed along or close to the belt, while spring bias acting on the cleaning roller firmly but yieldably biases the cleaning roller toward the blocking device. The spring bias and the blocking device are adjustable independently of each other so that the operating position can be adjusted to compensate for wear of the ribs while the spring bias remains unchanged. The cleaning roller is supported by composite spherical/rotary bearings that allow the roller to tilt. A hole in a frame plate accommodates removal and insertion of the cleaning roller lengthwise without disassembling the frame plate when the cleaning roller is to be replaced.