I am building an ICF home in NC.  We are to the point of roofing.  I am using a faux slate rubber shingle. The attic will be a conditioned attic with closed cell insulating foam. My question is this.  Do I need to install the ventilating channels between the rafters?  I am getting conflicting opinions. Some say that the foam sprayed directly against the roof underside will cool the shingles sufficiently, others say I need to ventilate the roof underside to prevent the shingles from overheating. Any replies are appreciated. 

I can't offer an educated opinion about the ventilating channels (other than the consensus in new building technology discussions seems to be that it's not necessary in most applications). But I was curious about your faux slate rubber shingle. Can you give us more details? Like manufacturer or maybe a link? Sounds interesting.

ventilating channels don't work! No need to install them. You are on right track with the conditioned attic.

My house uses a insulated attic with a 1.5" gap between the roof deck and the insulation. I use powered ventilation fans to constantly circulate the air through this gap. You can go on top of the roof on a sunny day and feel the heat just pouring out of the vent. You can definitely tell a difference inside the house as to when the fans are on or off. A vented roof should stay a lot cooler than an unvented, making your roofing last longer and your insulation doesn't have as much change in temperature across it, so that less BTU's leaking into your roof.

I would contact the rubber slate manufacturer and ask them how the warranty is affected by not venting.

I just remodeled my house this summer, we added two shed dormers to a cape in Maine and the Insulation contractor did not want me to use soffit vents (foam channels between the rafters venting from the soffit to the ridge vent).  They're recommendation was to not use any venting.  This did not sit well with me.  Also when I contacted GAF/ELK (shingle manf.) they recommended using soffit vents for extending shingle life.  I built with 2/10 rafters and used dense pack cellulose with soffit vents.  After much research and discussion I went against the recommendation of the Insulation contractor.  Now that it is winter I can see the direct result of my decision and I'm glad I went with my gut.

My ridge vent cover 75% of the ridge on my roof, the ends are not vented.  The sections that are not vented melt the snow much faster, thus much more heat loss.  These areas have a much higher risk of ice dams as well as a result of not being vented.  Looking back I wish the whole ridge was vented but not much I can do now.  I'm pleased with my decision and would personally recommend using soffit vents.  Not venting a roof structure is relatively new and I believe untested (10 years of results is minimal when you want you house to last 100+ years).  Venting has worked well for many years and I belive even with new insulation options still makes sense.