I'm not a physicist, but I believe this is not correct. First of all, because of various forms of friction (air resistance, tires' rolling resistance, and, to a much smaller extent, hub friction), a bike will naturally decelerate, i.e. it won't roll forever. As a result, we are constantly accelerating our bikes to keep it in motion, except when going downhill. This acceleration isn't much, but it's there. More importantly, weight certainly makes a difference when climbing.