a file deply job can save a backup of overwritten files with a .bak extension, but I've found no easy way to rollback (copying .bak files over original files) other than manually cp the files
I've run into this as well. I would submit an enhancement request for this functionality.
in your post- undo commands you can do the cp/copy
If you use a blpackage to do this, the rollback is built in.