I am looking at a project where I need to insulate and finish the interior of a pool house that has a gambrel roof. The building recently had the siding and roofing replaced (vinyl siding, shingles on top roof, metal on lower roof). It looks like there is a ridge vent in place, and they closed up the old gable vent. The second floor has vertical walls framed directly below the change in roof slope. There is air space above the wall framing that I think would allow for transmission of air between the two roof planes if it were vented. I didn’t think to carefully examine the bottom of those rafters bays to see if there was some kind of soffit venting. I didn’t see any daylight, so I’m thinking it is not open. 
Assuming there is no opening to draw air into the rafter bays and vent through the ridge, what is a durable way to detail the insulation of that space before closing it in? 

There are two dormers on one wall. Location is southeast PA, climate zone 4.

Thanks so much for the information and education you all provide on this forum!