General :: How To Recover / Root Filesystem From Backup?

Suppose I have a good backup of the / root filesystem. How do I recover the / root area? Suppose I have modified the root filesystem, perhaps I do an update some of the packages and regret it, and I want to get back to the system at the time of the backup. How do most linux people recover the root area of a system from a backup?

1) I wondered if I might put a System Rescue CD in and boot off it?
2) And then NFS mount the directory containing the backup? -In my case, I have made a good backup using rsync, to a directory elsewhere on the network.
3) And then, still booted off the System Rescue CD, mount the partition that contains the / root area in question?
4) Would I then clear or empty or delete the contents from the / root partition?
5) And then copy across all the files from the backup into the / root partition?

I ask these questions because of the (very nice) way linux OS is built entirely from packages... Am I being too complicated? (By comparison, I can see it is easy to recover user data.)If, instead, I simply recovered the backup straight onto the updated root filesystem, I wonder what it would look like if I then tried to verify it with "rpm -Va", for example? Surely, all the packages would fail the verification, because it would think it has a later version of each package from the update, but the actual files would have been overwritten by the earlier version from the backup?