I would suggest that you initially check that they are inflated to the correct tyre pressures as underinflation can not only cause noise but also tyre damage, especially to the sidewalls (little cracks in the sidewalls are a good indication of this and may result in tyre renewal if it is serious enough).
If the pressure is correct, check that the tyres aren't deformed with any carbuncles or odd lumps and bumps. Also check that they aren't twisted on the rims i.e that they are on straight.
If all of these checks are okay, I would suggest that you get the garage to check that the wheels are balanced correctly, as you may have lost a wheel balance weight. When the wheels in question were on the front, did you experience any wheel wobble or vibration through the steering wheel at a particular speed? This is often a sign of unbalanced wheels.
If you suspect a wheel bearing, jack up the car and rotate the suspect wheel as fast a possible by hand, any grinding should be evident.
After all of these checks, there is a remote possibility of wheel damage if you've hit a kerb etc hard. Otherwise I can't help. Good luck