Lucasfilm introduced the world of Rogue One: A Star Wars Story at Star Wars Celebration Europe on Friday. Director Gareth Edwards was joined by Lucasfilm president Kathleen Kennedy and stars Felicity Jones, Alan Tudyk, Mads Mikkelsen, and many others. In addition to the new footage, they covered lots of little new tidbits about the film and, at the convention only, they showed a new trailer.
Source: Gizmodo – Darth Vader Appeared At the Rogue One Panel at Star Wars Celebration