Normal in the sense of proper or normal in the sense of usual?
I was just watching a video of Olympic champion Ryan Lochte swimming backstroke, and I can guarantee you that his face stayed above the water at all times. And this makes sense, scientifically speaking. Your drag in the water is minimized when your body is perfectly horizontal, but if your head is bobbing up and down as you swim, that implies that it is not staying perfectly horizontal. Because of this, some backstrokers actually practice their stroke while balancing a cup partially filled with water on their forehead to make them more aware of any head bobbing that may be occurring as they swim, so they can minimize it.
If you are rolling to your hand lead sweet spot as your recovering hand enters the water, this should cause your hand to rotate so that your little finger is entering the water first, which will keep your hand from slapping the water as it enters, and that should help to minimize head bobbing.