From what you're describing, it sounds like the Fastenmaster HeadLok is what you're after.

I also used the GRK RSS jammies on a project involved mixed media a couple years back and was pleased with how they worked. No stripping is a really nice things. They cut through cleanly too. Pleasant experience.

If the budget allows, use those Fastenmasters, they're awesome. If I remember correctly, the GRK's are a little friendlier on the wallet.

 

How about Trufast? I used them on my last SIPs project but don't remember the pricing.

http://www.trufast.com/products/sip_nail/siptp.html

 

Check with a timber framing supply company. They have long screws in various lengths with rather large heads. Last time I needed them,I contacted Harmony Exchange,I think they are out of North Carolina.

 

I haven't done the roof build up yet, but on walls with foam bard I use Headloks through furring strips. I like that they provide all the engineering data for fastener spacing according to wind loads and cladding weight. (file:///C:/Users/work/Downloads/TER1009-01_20131218_HDLOK_Attach%20Cladding%20Wood.pdf). The Trufast has a similar report (http://www.trufast.com/links/pdf/TRU110910-21_Evaluation_Report_2015-08-12.pdf)

I couldn't find the same kind of design bulletin for over roof in north america. They have this guide in the UK (http://www.fastenmaster.com/tl_file...es/fastenmaster/product-info/headlok/SpecGuide/HeadLOK-Warm_Roof-spec-guide.pdf).
Doing a little digging, the only reference I could find for fastener spacing was in this article http://www.greenbuildingadvisor.com/articles/dept/musings/how-install-rigid-foam-top-roof-sheathing , which just says to use same spacing as wall recommendation unless you have lots of snow....which I have. So now I'm curious on how you're determining your fastener spacing because I think you're in a pretty heavy snow load area too?

 

Well, the head locks actually were cheaper than the GRK's. And they can be ordered in pretty much any length. As to how often the fasteners are being installed, I'm not making that decision. My "old Yankee" father is. I would go to an engineer on that but he's a penny pincher. I think right now he's at 16" OC for the roof.

 

It's funny. I'd be more worried about the sidewall than the roof. Especially with fiber cement siding. But asphalt shingles are heavy too[emoji849]