"Roll to pick up" is an objective in the sidequest Critical fail in Tiny Tina's Assault on Dragon Keep DLC
Walkthrough[edit]
Fight your way to the Northwestern portion of the Sacred Ruins and go over to the left. You will see a raised platform with the Crit sitting on it. Approach it and interact with it. Brick will roll his die to pick up the gun and get a fumble, or a 1. The gun goes flying off much to Mordecai's surprise.