It's WAY too early to be calling yet. The 'Buck Roar' (from what I've thus far read) has to be used carefully. I believe that it is a whitetail call though, but a rut-crazed mulie may come into it. It was designed and built from the sound a super aggresive dominante buck makes during those few days of the rut when they've entirely lost their minds. I would use it only if I knew that a big dominant buck was in the area. Otherwise, I fear, it will spook off most of the other bucks who already have their does and have no interest in sparring with a maniac!
If you do want to play around calling while the season is still new, grab a fawn distress call. I've had a number of does come into bow range while playing around with it, and sometimes there can be a decent buck in tow. If you can, use a fawn decoy to instantly double your chances.
Good luck getting your first bow mount mulie. Just chill out for a bit and let nature take it's course.
Tree