I'm in Seattle area. While not super cold in general, it is super wet!
I have used screws into the metal ribs, but then I covered them with silicone to break the thermal bridging effect.
My main problem has been the actual interior of the roof skin and the curved roof ribs.
I'm not seeing issues with my vertical ribs/skin or much even on my windows.
I'm using rigid foam, then I screwed wood stringers with thin foam between the stringers and ribs. I didn't see one screw condense, but boy the ribs and skin sure did!
One thing that may be part of the problem is I put the aluminum side of the rigid foam against the skin. I'm going to flip that. The next is that the rigid foam doesn't really conform to the skin and leaves gaps between the skin/ribs an the insulation. So, I'm thinking of putting wool insulation as a backing to the rigid and stuffing it in the gaps around the ribs and rigid.
That fills the cavities made by the rib grid, but it still leaves the bottom of the ribs exposed. I'm not sure how I'm going to cover all of that.
If I wasn't as far along with my interior build and had the money, I'd spray foam. Hindsight.
I think (hope, pray, beg the bus gods) that once I cover all the ribs and put up the ceiling it will create a good thermal bridge.
I plan on using some kind of dehumidifying.
I'm also hoping that when I paint the roof with elastoseal that it provides even more of a thermal break.
Oh, per the Reflectix insulation, the company states that it needs 3/4" air space between it and any metal to avoid thermal bridging.
Hope this helps.