@classmethod
def rollback(cls, resource, background=False):
    """ Rollback a disk from a snapshot. """
    disk_id = cls.usable_id(resource)
    result = cls.call('hosting.disk.rollback_from', disk_id)
    if background:
        return result
    cls.echo('Disk rollback in progress.')
    cls.display_progress(result)
    return result
