ᐅ To ventilate a cold roof or not, which design is best, and what are your experiences?

Hello everyone,

I have a question about cold roofs.

We are building a house with two full stories (two concrete slabs), a small knee wall of 25 cm (10 inches), and a 25-degree pitched roof. The upper floor ceiling will be insulated with wood fiber.
The roof structure itself consists of tiles, counter battens, battens, underlay membrane, 24 mm (1 inch) sheathing, and rafters.
I often read in connection with such a construction about a ventilated roof, meaning an airflow between the rafters into the attic and exiting through the ridge.
Is this ventilation necessary for this type of roof assembly?

Ventilated means that it is always nicely dry at the top. I have two ventilation openings in the gable (but also a wooden beam ceiling without a vapor barrier/vapor retarder).