If the roof is stick framed (which i think it is) it is supposed to have ridge support every 4 feet running from a load supporting wall/beam up vertically to the ridge..,,,where the dormer crashes into the main roof should also have support to a load bearing wall...whereas the ridge for the dormer has none and should have at least one support other than the main roof rafters and gable wall.. you can spread the load over the ceiling joists for the dormer but ideally there is a patrician wall under it ... as for the engineering ...i think i read that the house was 18 years old...its only within the last ten years that a house print had to have a BIN stamp on it for residential ...so it most likely was only inspected by the building inspector of the time...but the town will have a copy of the original prints that the building permit was issued under...Im guessing they put collar ties but no vertical supports for the ridge....
IF it was a truss roof the sheeting would have to be continuous for the length of the roof on the rafters where the dormer sits...i cant see any sheeting or ribbon ties at the back of the exposed dormer...thats why im guessing its a stick frame