ᐅ Insulation for ventilated roof tiles and the roofing process

Hello everyone, I hope I’m in the right place here 🙂 We want to convert our attic and insulate it from the inside. It is a timber-framed house with a standard gable roof, one side pitched at 45 degrees and the other at 55 degrees. Currently, there are roof tiles installed that I am not familiar with. A roofer I know told me that I am not allowed to insulate underneath them because they are internally ventilated tiles.

I’m uploading a few photos here; maybe someone can tell me something about them.

My question is: Are the red and brown tiles both internally ventilated tiles, or are they the same type? It seems that the dark brown ones might be a different construction.

It would be great if someone could possibly explain the characteristics of internally ventilated tiles and what the outcome is when insulating beneath them.

If your acquaintance is a professional, why don't you trust their statement?
What can anyone here in the forum identify based on just 3 photos? Especially since they are all taken from outside?
Good luck!