New construction home.  1/2 CDX on trusses, then Gaf Deck armor, then 2" rigid foam, then 1/2 cdx , then gaf deck armor and roof material.  

My question:  I can get 2" rigid foam with black craft paper facing for a very good price.  With all the different foam facings foil, no-face, plastic, paper, etc.  What should I use, and what is the applications of different foam facing? 

Why two layers of Deck Armor? That stuff is kind of expensive. I'd also only use it if you have roofing material that breathes (top vent), seems wasted otherwise. I assume that you are doing insulation also against the bottom of the roof deck, I think folks here are going to need more information about your plans there.

So I have a vaulted ceiling and what is attic I will do conditioned and insulated.
I will lay some type of material over cdx. What I am really after is
what the rigid foam (iso) with black felt or craft paper is used for?
Thanks for the reply. Suggestions welcome.