Perhaps slightly unusually this house has a custom made roof frame of steel beams and more traditional timber down rafters.
The arrangement is serving its purpose of supporting the roof tiles of what is a brand new house.
Note that the tiles are underlined with a breathable sheet membrane which provides a secondary barrier against rain penetration whilst allowing the roof space to “ breathe”. This helps avoid condensation build up it the attic.
Note also that the ceilings are insulated with a foam sandwich more commonly seen on roof undersides and external walls. It provides a good alternative to more widely used fibreglass.