Yeah, I can do tomahawks just fine.  It might help to practice with a full-size frisbee first - they tend to do it easier.  You definitely do have to release it nearly "flat" to the ground though, vs perpendicular to it, or you're right, it'll just turn into a roller.  Start the throw with the disc up and down, and end the throw with the disc flat, upside down.  If that makes sense...