Just tried this on a recent Trixie amd64 install. locate isn’t installed by default, but there is a locate/stable 4.10.0-3 package and it installs just fine for me.

sudo apt update
sudo apt install locate

Is it possible that you didn’t enable snapshots during installation of TW, and then turned it on later?

That seems to be a common explanation on the openSUSE forum when .snapshots is missing from fstab (found by searching for the error you are hitting). There are some threads with workarounds. Basically, mount the .snapshots subvol manually, re-try the rollback and then add .snapshots to fstab so it works in the future.