Ellis Amdur

You can roll over your shoulder (the arm that is "locked") or, draw the elbow inwards towards your abdomen (this move comes from under the shoulder blades). The roll-out works quite "late" in the technique, the elbow-inwards must be done earlier.
Of course, if you allow the lock to be fully applied and your arm fixed and locked, then all you can do is drop - and depend on the forebearance/decency of tori when you tap out.