Hi roel there are two types of insulated roofs vented and unvented each with different possibilities for insulation.
Rockwool insulation roofing.
Based on his knowledge of energy efficiency and sustainability of overburden assemblies he was recruited by rockwool in 2018 to advance specifications of stone wool insulation for the low slope roofing industry as a technical sales specialist.
Rockwool stone wool roof insulation combines the thermal performance dimensional stability impact resistance and acoustic control required to increase the performance of many flat roof assemblies.
It has excellent acoustic properties.
Rockwool comfortboard 80 is a rigid mineral wool insulation sheathing board that is non combustible water repellent fire resistant and sound absorbent.
Joe donnelly has a long history in sustainable roofing design and construction.
If you have an easy roof to vent and decide to go that route you could use mineral wool insulation between the rafters and beneath the vent channels.