TLX Gold as underlay for re-roof

I have a roofing company that has specified TLX gold permeable membrane under the tiles as a substitute to top up of insulation layer above the ceiling. This is high tech and fully breathable membrane However I have a query about adequate ventilation in the roof space. Do I still need to have vented sofitt. Effectively it makes it a warm roof rather than cold. I have not used such material before.