Sometimes, weapons are made so accuracy is not a top priority. Roller fills that spot with simplicity. It will roll across the ground in whichever direction it was fired (or lands from) and will do a cool 20 damage.
What's better than a weapon you only have to aim moderately accurately with a likely chance of hitting? A weapon you only have to aim moderately accurately with a likely chance of hitting that does double the damage! Although it does double the damage, be careful because it doesn't travel as far on the ground.
Much like it's predecessors, Groller rolls across the ground, but as it rolls it grows larger and larger, building up damage. When it reaches the final form, it will deal 48 damage.