Basically any of the ones that look and act like guys probably are. Its not hard to tell a mans man from a queer. Just look at the way they talk or act around other dudes. Now, I personally feel the bodybuilders that only focus on symmetry, aesthetics, looking 'pretty' and how dark their tan is are usually the questionable ones. The ones that focus more on power training, heavy weights, mass and density are more than likely the straight ones. But again, what the fuck do I know.
Definitely Str8- Warren, Dennis James, Dorian, Cormier, Wolf, Ronnie, Priest...? and Ruhl to name a few.
Not to sure about the rest!