Loft ventilation tiles

lukekelly19

I am looking to have some loft insulation put in. I've been told that ventilation tiles are also needed to avoid damp. My loft currently has stud walls all around and on the ceiling of the room. To install the insulation cheaply, I would only have holes made in the side stud walls, leaving the ceiling walls. Would these have to be removed to install ventilation tiles? Or could the roofers just 'punch through' a small bit?

Any thoughts/experience on ventilation tiles appreciated!