I just did a beadm rollback, the machine crashed, and when rebooting, all snapshots that were taken after the rollback have disappeared, is that expected behaviour?

veg: that's how zfs rollback works (beadm rollback is a thin layer over zfs rollback).

veg: if you want to preserve the newer snapshots, something like "beadm create -e currentbe@snapshot rollbackbe" should work - it creates a zfs clone of the snapshot (a writeable filesystem with initial contents from the snapshot).