What makes a good rollback in reining?

A good rollback starts from a straight, balanced stop, turns cleanly and efficiently over the hindquarters with free and active shoulders, and departs willingly on the correct lead without the rider needing to reorganize or restart the horse between the elements. Each component of that description is a training indicator as much as a performance requirement. The stop that initiates the rollback must be straight because a horse that stops crooked arrives at the turn in a compromised body position — one shoulder will be loaded more than the other, and the turn will either fall through the low shoulder or lock up on the high one rather than sweeping cleanly over the hind end. The turn itself should show the horse's shoulders moving freely and actively rather than being dragged through the arc by the rider's rein — a horse with correct shoulder control turns over its hocks because its front end is light and mobile, not because the rein is pulling it around. The hocks stay as anchored as the speed and mechanics of the maneuver allow, serving as the pivot point for the 180-degree arc. The departure out of the rollback should be immediate and willing, the horse driving forward off the hind end onto the correct lead without hesitation, stumbling, or requiring strong encouragement from the rider. A horse that pauses too long in the rollback has lost the forward intent that makes the maneuver fluid. A horse that jumps forward without completing the full 180-degree arc has prioritized the departure over the turn. A horse that falls through the turn to the outside shoulder has lost the body control and collection that the maneuver requires. The rollback that scores highest is one where all three elements — stop, turn, departure — appear to happen as one continuous motion driven by the horse's own willingness and athleticism.