If it's a finished attic, then I presume its just ceiling drywall,
rafters with insulation followed by the roof? If that's the case,
there should be a means for hot air to exit at the top, usually a ridge
vent. There should be continuous soffit vents under the lower roof.
If they did that right, then there is hope. But the final thing needed
is air channel baffles which should have been placed below the
sheathing, before the insulation was applied. That keeps a path open
for the air to flow. If they didn't do the first two things right,
there is little chance they put the baffles in. And if they didn't,
the insulation will fill the space, giving you no air flow. It's also
not unusual for these conversions to be done with only existing 2X6
rafters, which leaves too little space for the right amount of
Tinting on the sky lights will help cut down heat from the sun. I've
seen DIY kits at the home centers or you can have it done
professionally. But I'd have to agree with Edwin, that in RI in the
summer, I think you'll want A/C, especially on an upper floor.