Metal Roof on Florida Eichler???

Here's the problem:

I purchased a home that originally had a shingle roof that was replaced by a metal roof. The home that is currently being renovated has a cathedral/vaulted ceiling with no attic space. The ceiling is exposed as of now and only has space for R-19 insulation between the joists.  I am afraid that with no way for air to escape the homeowner will destroy the metal roof and the Sheetrock that will be installed after the insulation if the roof is not properly vented. I have provided photos of the soffit vents at the edge of the overhang that are still open but there is no venting from the inside(between joists) for the air to escape at the top of the roof. I assume venting was closed after the shingle roof was replaced by the metal roof.

What is the best way to provide ventilation to this roof? Is it possible that the metal roof is being vented between the plywood (underlayment) and metal roof itself? Should the homeowner just install the R-19 insulation and proceed to sheetrock application?  Is their anyone aware of a solution or can provide a referral? 

Your assistance is greatly appreciated!