The straight-bar wrist roll-up is a movement targeting the muscles of the forearms and hands. It is normally performed in high reps, for time, or simply to failure as a burnout for the lower arms. If shoulder fatigue limits your ability to perform the movement, it can be done with the barbell resting in a rack.
Builds hand and wrist strength
Builds forearm size and strength
Doesn't require unique equipment
If grip strength is a limitation, lifting straps allow heavier loading