Dwayne Johnson is in discussions to join the cast of G.I. JOE: COBRA STRIKES, reports Deadline.com. He's up for the role of Roadblock, the heavy machine gunner and cook. Channing Tatum is expected to return as team leader Duke, but villains Joseph Gordon-Levitt and Sienna Miller are unlikely to return. Jon Chu (JUSTIN BIEBER: NEVER SAY NEVER) is directing.