It rollsback to that point when that snapshot was taken. If its a snapshot appdata it will rollback everything to that point when the snapshot of appdata took place. Its might be better to have a dataset for each app in your appdata share that way you can rollback specific folders. You can also go into the snapshots by browsing the .zfs folder at the root of a dataset. Its hidden by default but you can just pull files from it if you want. Its read only so it cant be modified.