2006 F-250 Viberation????

I have rotated tires front to rear and side to side with no change.. This is a 4WD drive vehicle but hasn't been off road while I have had it.. Rims are clean on inside.. Since I am planning on a trip soon, and I have a service contract on vehicle, I took it to a local dealer today for assessment.. Findings: Ball joints are good.. U-joint seems fine..front wheel bearings feel ok.. but after a drive on the freeway, the shop service person did acknowledge the buzzing vibration at 45-60 mph on freeway..they suspect failing front wheel bearing but vibration analysis will hopefully locate the location / source of problem on Thursday.. thanks to all who have responded with excellent ideas.. I will update as soon as problem is fixed in case anyone else has this issue..