This weapon is Roller if Roller looked in a slightly color-warped mirror. Back-Roller does exactly what you'd expect: It rolls backwards! and deals decent damage too making it a great weapon for the starters in the game!
Overshooting your target may not always be a bad thing. Heavy Back-Roller will make room for your tendencies to estimate incorrectly to not be in vain. The upgraded tier has double the damage and bigger the 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. Figuratively it moves forward in maturity, but still rolls backwards. So, is it progressive or regressive? You'll figure it out. This tier is a more risky weapon than the previous tier since it can go either better or worse depending on how long it was rolling, it deals 5 damage at the least size and 48 on the biggest size. Use this more wisely than the first and second tier.