what is roaring noise after 20 mph.sounds like low flying plane wheels are tight

Wheels are tight because of binding brakes. Does the "mechanic" say why they are binding? The noise could be almost anything spinning at the front of the engine. Have the "mechanic" listen with "mechanic ears" for the noise when rev engine. If only happens when moving then fix the binding first and see if noise goes away. More specifics and detail would help when we try to figure out what you are saying.