Is there moisture on your car too? Is there moisture on other parts of the roof? I would guess that this is just normal dew if you answered yes tho these questions. Can you get into the attic? If your insulation is in the floor of the attic, as opposed to the roof, then the inside should be somewhere close to the same temp as outside, especially if there is no sun beating down on the roof heating it up. If, at 6 in the AM this is true, then you are probably ok.