Mebbe the powered vent idea would require some control sophistication to turn it on at right times (sorry), but a passive gable vent could also be opened/shuttered from the floor with the right hookup. (Farmtek or somebody?) If your building is pretty air tight you'd need some inlet too, say up a ways on the sunny side and shielded from weather surprises. Dutch445 says the ceiling fan works, and IMO that's a big +1. It's an option, but venting the building somehow is a must most anywhere you live, no? .....
Condensation above your insulation can be scary. Having it at the flat ceiling vs between upper rafters allows easier venting/inspecting. I've seen insulation so close to the roof deck on a new house that lack of circulation led to condensation and black mold galore on the rafters within two yrs. The entire deck had to be stripped off (sawed out between joists) everything treated with some spray (iffy IMO) stuff and several I-joists replaced. 2x4s were added on top with gaps to vent laterally and increase what little airspace there was between the f'glass and an entirely new deck. btw: this house had a seamless rubber roof the was fully intact and in-floor heat on the main floor and in the basement slab.
We discussed powerventing up-slope from channels added along the eaves, but ....... we feared that moist outside air might condense under the deck as before. I haven't seen the house in 2ys since the fix. I'd be afraid to and wouldn't bet that another 1 1/2" or was enough space either, but I hope so. I'd have had lower ceilings, say 9' or 10', more roof pitch, and a lot more room to ventilate or circulate above the insulation.
Sorry, wraiths if I misunderstood exactly where/how your insulation is installed, but the long story came from fearing a repeat of what I'd seen.....