Air flow for cladding and flat roofs

I'm after some thoughts on my cabin roof / wall junction. 

I want a clean line i.e. not a roof overhang with facia and soffit.

Question is would a gap at the top be sufficient for air to flow and allow the wall to breathe.

This way I can rid myself of the 

Need for expensive trim and keep the look clean.

Build. 6" stud with warm roof.

Clad in larch. Rubber roof on 120 fibre coat insulation.