While getting the xmas items out of the attic, the underside of the roof seem damp in spots. it was below 30 last night and we had a frost. The damp patch was on the late morning side. The roof was replaced last year and we had no problems with it (at the time a roof line vent was put in). We also blew in more insulation. Could the damp patch just be morning frost or could it be a new repair job...

there are three possibilities.
1. Improper ventilation- did your insulation cover up the venting at the bottom of the roof?
2. Excessive moisture escaping from the inside of your house.
3. Your roof may have some small leaks.

A simple inspection on your part should uncover the problem. HAVE FUN!!!!