Ive never had to rollback a MacOS update or upgrade. I dont think a lot of Windoze users can say that.
That's why I only run Windows in VMs (virtual machines). Prior to doing updates, I make a spare copy of the VM disk file. Then I run the updates. if it looks like trouble, "rollback" consists of copying the spare file back over the updated one. No fancy procedures, just a single file copy.
As it happens, I'm holding off on updating my Macs to Catalina because it removes support for all 32-bit applications and services, and I have a couple programs that aren't yet available in 64-bit versions. If I allowed my Macs to update, I'd have to roll them back.
And that's what "Time Machine" is for. :-)
I’ve had to rollback Mac OS. Not an easy thing that’s why running Macs in a corporate environment is tough. Now Joe blow on the street probably has little need to roll back Mac OS update.