Sam Rockwell is in talks to star in a biopic of country singer Merle Haggard that would also find the Oscar-winning actor doing his own singing. Amazon Studios just acquired the package, which finds Robin Bissell directing from a script he's co-writing with Theresa Haggard, Merle's widow. The two of them will also produce the film, which will be based on Merle Haggard's memoir Sing Me Back Home -- also the title of one of his biggest hits. Deadline broke the news, reporting that the story will be set in the '60s and will focus heavily …