Eagle-eyed Ringers spotted Royd Tolkien in the Desolation of Smaug Extended Edition.  You can see him here in this scene between Gandalf and Beorn discussing the tombs in Rhudaur.

And confirmed by Royd himself via his Twitter feed 🙂

Is this a cameo in The Desolation of Smaug Extended? (30 seconds in?)

Yes 🙂