Finalizing details for our framing contractor who starts in a week. We are doing cathedral ceilings throughout the house. We are in zone 3 in the SF East Bay, R-38. Based on reading here and several other sites we should go with ventless cathedral ceilings because we have dormers.  I prefer to use Rockwool over EPS foam insulation because it can be recycled and if it ends up in the environment from cutting not as big of a polluter. 
Rafters are 10″, will be filling them with either densepack cellulose, denim or something similar with R-4/inch. This will give me the R-38 before adding in the insulation above the interior sheathing. Martin’s article says R-5 rigid foam for zone 3 above the inner roof sheathing. My question is it ok to use roxul comfort board in place of the EPS?
Thank you
Eric