A location would help.
You can see mine at left. Down here where it gets both hot (mid 90s) and humid (also mid 90s) for days at a time, many months of the year, ventilation is FAR more important than insulation - though insulation would (theoretically) help mitigate my brutal sun pounding down on the roof of my hen house. I also have heavy breeds not famed for heat tolerance, including CornishX and Dark Brahma (my errors, I'm breeding away undesired traits)
I use a galvanized metal roof for cost, for ease, for durability, and because it reflects much more heat than it absorbs (something that can't be said of any shingled roof) and doesn't trap heat, greenhouse-like, as a polycarbonate panel would. Passive airflow designs with good overhang and a ridge vent ensure cooler, drier air is constantly moving upwards along the underside of the metal roof, pulling warmer, wetter, ammonia-laden coop air out with it, while also cooling the underside of the roof, to reduce radiated heat. The relatively low mass ensures it doesn't long buffer temperature changes, either. As a final benefit, brief visual inspection allows me to see if there are any leaks (rain is my big concern), since the "guts" of the roof structure are in full view. No hidden damage.
There **may** be a situation where an insulated coop is worthwhile, and its ventilation designed in a way that the insulation is necessary, effective, and yet does not inhibit the extraction of warm, moist, ammonia laden air from the coop - but it is not the norm.