Improved boat bumper assemblies are provided which include upright, rotatable, synthetic resin rollers rotatably mounted on stationary uprights located adjacent the sides of a boat slip. In one form, the bumper assemblies are mounted either as original equipment or as retrofits directly onto roof-supporting stanchions of a boat mooring structure; alternately, standoff bumper assemblies may be used, having rollers rotatable on uprights and supported by spring-biased, resilient connection structures.