if the T&G is green it will expand/contract until dried out, no matter how many nails you put in it. I always use min 3 nails in each truss..
I was referring to IKO and BP (only brands my supplyer sell), as thats what the customer usually want on there roof because of price.
In my opinion if the T&G has gaps between the boards its better to use plywood over it. I had always use T&G for the roof until the warrenty issue. Now I only use 5/8 plywood.