What to consider
Underlay drains incidental water outwards; vapour control limits moisture movement from inside. Ventilation paths must remain effective at eaves and upper details. Use compatible tapes and collars around penetrations, and distinguish roof ventilation from room ventilation.
Apply this to your roof
Record your preferences in the roof plan. Final dimensions, product suitability and the complete build-up are assessed for the actual roof; keep the agreed details and manufacturer instructions with your project documents.