Why vent the roof above a room on the top floor?
This topic interests me, thanks for posting it. Just don't call it pre-vent shun.
What are you venting?
I see 5 things needing to be vented: plumbing, gas appliances (furnace, clothes drier, water heater), fireplaces, radon, and living space air.
IIRC codes require all, except living space air and the drier, to vented out the roof.
In the attic, I recall vents in the soffit which supply the air in and then a larger vent out. The soffit vents should not be covered up with insulation. My climate is dry, but I suspect condensation and summer attic heat are both mitigated with the venting.
I do not see what venting in the walls would do. That might make the house into an envelope house. I don't think that is a retrofit task, but an initial design and construction project.