"Roll to pick up" is an objective in the sidequest Critical fail in Tiny Tina's Assault on Dragon Keep DLC
Walkthrough
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.