Plain English Meaning
Rollout is the act of leveling the wings at the end of a turn. The pilot uses the controls to bring the airplane out of its bank and back to flying straight.
Full Definition
The control input and resulting maneuver used to return the airplane from a banked turn to wings-level flight, by smoothly applying aileron and rudder opposite the direction of the turn until the wings are level and coordinated flight is reestablished.
Context Anchor
Used during level turns when the pilot is bringing the airplane back to straight-and-level flight on a selected heading.