I have had the foam insulated roof/ceiling up for two winters going on the third, there are no zero indications of any moisture anywhere.
You need to know which code, and version of code, applies to your area. Code is updated generally every 3 years, but some places still run on earlier versions, not the latest. To top that off, states and towns can add additional language to make certain parts of the code more restrictive. Coastal. Seismic. Or simply over-controlling AHJs. With all that?
I'll preface that everything I write that follows can be picked apart, I'm simply addressing the basics:
Find out what code applies to your build. Have printed pages of that code, or bring a laptop opened to the link (or the proper link) I included below. Bring them in to your inspector. Have them interpret the wording for you. They can only do that if they know how your roof is built. I've had one decent (actually stellar) building inspector in my area. Since he retired, I've usually known more about the code than any of his subsequent replacements. Seriously.
1202.2 is the overall section that deals with roof ventilation. Read
carefully to get to the subchapter that applies to your build. Language can be nuanced and confusing. Don't read a sentence and think "Ah hah!" Read the entire chapter as well as any included attachments.
1202.2.1 addresses "ventilated attics and rafter spaces". It's typically referring to roof rafters filled with air-permeable insulation (FG batts for example) and addresses the need to leave an air gap in each rafter bay between the top surface of the insulation and the underside of the sheathing. Again, there are other situations as well.
1202.2.3 is for unvented attic and rafter assemblies. Unvented these days, the most common that I see is closed cell foam sprayed into each rafter bay with the foam being in direct contact with the underside of the roof sheathing. But again, there are other assemblies that meet that wording.
To help you present better, know what foam you have; open or closed. Know the thickness of the foam application. Is it between the roof rafters? Is it in the "attic floor", or the ceiling of the living space below the attic?
Be familiar with soffit and ridge vents. Gable end wall vents. Classes of vapor retarders.
Know where the thermal envelope of your house is and if it includes the attic space or not.
Inspectors deal with messy builders. Show up with a good attitude, be prepared with your build details (a basic hand drawing can help in addition to your words) , have a basic knowledge of terms, and bring an inquisitive mind. The inspector should be able to show you in the code why you have to do what he says you have to do. If he can't? "Hey, I'm still a bit confused...is there anyone else here I can talk to so I can get the details right?" For clarity, ask if they have a copy of the IBC Illustrated Handbook in the office, so he can show you pretty pictures. When language confuses, sometimes pictures can bring clarity.
Anyhow, I hope this helps more than confuses. For your reading pleasure, here's a link to
Chapter 12.