There is a bit of comment regarding different versions of roof ventilation in the following topic that may help
The following I can recommend (particularly the roof and ceiling insulation rather than just the ceiling):
Getting insulation will make a big difference to your comfort, have you thought about splitting the insulation (2.5 and/or 2.0 batts) to put batts on the roof underside and on the ceiling, this may provide both noise reduction and reduction of cavity heat.
I have no recommendation either for or against about the following but it does show options regarding thermostat control and after dark operation. I am sure there would be similar in most brands
We did look at the Solar Whiz units on our previous house (whirlybirds were getting old) but have just moved into a new home and have split the insulation, and are awaiting summer to see if we need venting here or not. We do have ducted AC so we way up cost of the heat load and performance. If the cavity load isn’t too high we may not worry.
