I wouldn't rule out the bearing. If the rotors were replaced, couldn't the bearing have been over tightened, when the rotor was reinstalled? I have had wheel bearings go several times over the years, and they always let me know by making a high pitched noise. It can be dangerous, as a frozen bearing can damage the spindle. Sometimes it can cut the spindle right off. Get it checked right away to rule out a frozen bearing. Good Luck