I am building an 88 square foot office studio that I would like to be sure it is well insulated. Here’s a picture of it: http://www.summerwood.com/plans/home-studios/catalina/1045/detail.html

My question is how to properly insulate the roof.. As you can see from the picture, it has 5 sides and the roof has a single peak. The rafters will be built with 2x8s. I am planning on sheeting rocking the inside ceiling. Should I:
1. Insulate with batt FG insulation between the rafters and install soffit vents in the eaves to be sure the roof is properly ventilated along with ridge vents along all 5 of the ridges?

2. Put rigid insulation on the outside of the roof sheathing and then add another layer of sheating to nail the roof shingles to..but do this with-OUT ventilation?

3. Other options?

I’m really stuck on this one so advice would be much appreciated.

I live just outside of San Francisco, so fairly temperate climate but I do want this studio to be comfortable especially on cold/rainy days.

Thanks in advance!
tom