posted pictures and short bios on the main characters of the movie. As the cover confirms, Darth Vader will be in the film but not as the main villain. I suspect his role will be small, mostly demanding updates, action, and eventually unleashing retribution on Empire commanders once its clear the Rebels get away with the Death Star plans before taking charge of the chase which will provide a nice bridge to the opening of A New Hope. B elow is my even shorter description of each with head shots of each in character here.
Jyn Erso (Felicity Jones) - described as becoming "a kind of Joan of Arc in the story."
Captain Cassian Andor (Diego Luna) - "a by-the-book Rebel intelligence officer, brought in to steady the volatile Erso..."
Chirrut Imwe (Donnie Yen) - "Pronounced chi-RUT, he’s no Jedi, but he’s devoted to their ways and has used his spirituality to overcome his blindness and become a formidable warrior."
Baze Malbus (Jiang Wen) - "Heavily armored ...he is devoted to protecting his friend Chirrut at all costs" but doesn't really believe in the Force.
Bodhi Rook (Riz Ahmed) - "Rebel squad’s lead pilot. He tends to be hot-headed, but any abrasiveness is overshadowed by his skills in the air"
K-2SO (Alan Tudyk) - "the antithesis of C-3PO."
Galen Erso (Mads Mikkelsen) - "Jyn’s estranged father is like the galactic version of nuclear pioneer J. Robert Oppenheimer, with doomsday knowledge that is sought by both the Empire and the Rebellion."
Director Orson Krennic (Ben Mendelsohn) - ambitious smart Empire leader who wants to destroy the Rebellion
Saw Gerrera (Forest Whitaker) - Same character as one from Star Wars: The Clone Wars season five as a young man who fought with Anakin Skywalker against the Separatists droids. Now 20+ years older, his experiences from the Clone Wars to fighting against the Empire has turned him into a radical that the Rebellion leadership doesn't really trust (and he doesn't trust them) that is willing to go to extreme measures to do what he thinks is right.