Overshooting your target may not always be a bad thing. Heavy Back-Roller will make room for your overestimations. The upgraded tier has double the damage and a bigger blast radius for more effectiveness, giving you more reason to use this weapon if you don't know where to aim.
Back-Groller is quite a paradox. It rolls backwards, but grows. The bigger it is, the more damage it does. This tier is a more risky weapon than the previous tier, since it can do either more or less damage depending on how long it was rolling. It deals 5 damage at its smallest and 48 at its largest. This tier should be used more wisely than the first and second tier.