Via Ign.com:

Marvel Comics will release a Rogue One: A Star Wars Story comic ahead of the movie. Marvel confirmed to IGN the comic is a lead-in to the film, and not an adaptation.

During the Diamond Comics Retailer Breakfast at C2E2 in Chicago, the company revealed the series to be three issues plus a one-shot. The Rogue One: A Star Wars Story comic is set to release in October. No further information was given.

Rogue One: A Star Wars Story—the film—will debut in theaters on December 16, 2016. Directed by Gareth Edwards, Rogue One: A Star Wars Story is a prequel to Star Wars: A New Hope, and tells the story of the resistance fighters who’ve united to steal the Death Star plans from the Galactic Empire.