If you start DeployJob from pre-defined BlPackage and you need to rollback. However, the pre-defined BlPackage had been deleted. Would the rollback process work?
what do you mean by 'pre-defined' - the blpackage must always exist to perform a deploy. you won't beable to remove the blpackage w/o removing the deploy job, and if the deploy job is gone (or the history of the deploy job run) you won't be able to rollback (because the objects will be gone)