Well after about a month of my roof rattle getting worse, I started to explore different remedies to fix it. Well today I found it and fixed it. The rattle sounded like it was coming from the upper rear corner of the passenger side roof. I tried everything to isolate it! Spray lubricant, shimming under the loose plastic trim pieces, etc., but this didn't work. It just so happens that that rattle was not the roof. The tonneau cover was loose on the passenge side. I found it by pushing the front of the toneau cover up (with the door open). It was loose and it made a noise when I moved it up and down. I then went to the drivers side and tried to push the tonneau up and it didn't budge. The drivers side didn't rattle so I figured that the tonneau being loose must be the problem. I then opened the tonneau to the point just before the roof started to go down into the roof well. I then looked at the forks that lock the tonneau down when it is closed. I noticed that the 2 10mm bolts on the passenger side looked like they had been adjusted by someone. I took a 10mm socket wrench and loosened the 2 bolts that hold the forks on the tonneau cover (but not too loose, leave them snug). I then took a rubber mallet and lightly tapped the fork up towards the tonneau cover about 1/8 of an inch. Then I tightened the 2 bolts back up. When I closed the tonneau it was now just as tight on the passenger side as it was on the drivers side. Then I took her for a test drive on bumpy roads and guess what? NO MORE RATTLE!!! Hope this helps others with there rattle problems.