I have a flat roof shop with an upstairs I would like to finish off.  It is not practical to vent this roof in the normal manor. I have a parapet wall on three sides and putting a roof vent into each truss bay is not in the plans, trusses are solid with a top/bottom chord.  My idea is to spray foam insulate against the roof and vent what is left inside the structure with a continuous vent along each inside wall.  The appearance doesn’t bother me but is this a good idea?  What other ideas for venting this are out there, or is it acceptable to simply sheet rock the inside and forget it?  This area will be heated as a finished structure.