I had a wheel bearing replaced at about 50k miles, it was covered under powertrain warranty. My car would make noise on the highway when I went straight, and increased as I veered left and all but went away as I veered right.
A warped rotor I usually feel rather than hear. The car tends to surge as you stop as it brakes less/more/less/more very quickly.
So as to the actual cause, does the sound occur during any driving condition, at speed, while turning?