Get a second opinion or look at them yourself. I have personally put 50,000 on my rotors (bought truck with 68,000 so can't say if they were changed before I bought it). No problems. Is there any sign of problems during braking, like shaking, pulsing, grabbing or grinding. If not, you might still need brakes but the rotors are probably fine, as long as they are still above the minimum thickness spec.
Don't know what rotten means. Might mean that they are very rusty with big chunks flaking off in the center vent area. I have seen this on Chinese rotors on my Ranger now that we use salt on our roads in the winter.
All that being said, brakes are a very important safety item and should be made right if they indeed need service.