Don't listen to morons.
Check your tires... you may have a broken belt in your tire or a 'knot' on the tire.
And yes, brand new tires straight off the shelf have been known to have broken belts.
By the way, the belts are the steel wire rings that circle the entire tire. There are many of them and it only takes one breaking to make a considerable difference in performance.
And a 'knot' is simply a rupture, or weak spot, in the tire that allows air to enter that area and balloon it out... like a knot.
But for starters, try rotating your tires.
Front to back ONLY. Not side to side... some tires have directional patterns that can only go on the wheel one way or severe tire damage will occur.
If you notice a difference, perhaps in the direction the vibration is imminating, it's probably the tire.
Another possibility: Have you used any fix-a-flat or any other tire-injectable chemical in your tires? That fix-a-flat stuff never leaves the tire(unless you have a huge hole in your tire) and dries in mass to a location inside the tire and causes a significant weight balance problem. You can't solve it by balancing your tires because the 'dried cake' of this crap moves around inside the tire.
But unless you've had an accident, there should be nothing wrong with the mechanical portion of your car.
The rotors only need replacing if they show significant wear, such as, deep(1/16", 2mm) scrapes... the rotors should be relatively smooth with no deep scars; or if the rotors are warped, possibly from overuse at highspeeds heating the rotor to extremes and cooling it too fast... such as running through a puddle of water. Or of the rotor is too thin. If you look from the top down on the thin side of the rotor(such as looking down if it were mounted on the car) you will see two thick sections with a grid like structure in the center. Kind of like an oreo cookie. Those thick sections should be at least 1/8"(3-4mm)thick. However, the thickness wouldn't cause vibration. Only if the rotor is warped will it cause a vibration.
But if you have problems with the tires, it will 'echo' through the car and cause the soft rubber grommets supporting your brake and gas pedals to vibrate.
But if none of this stuff works... try another(well known... retail) mechanic.
Honest mechanics are like lawyers.
Personally I think it's your tires.
