Right, but energy that would have heated the roof goes towards powering the aircon (which likely is on the roof itself), which then emits the same amount of heat, no?

Say a roof is absorbing 10000 watts. You install solar panels that absorb 2000 watts, used to power an airco. You now have your roof absorbing 8000 watts (released as heat) and ann airco absorbing (using) 2000 watts (also released as heat). Am I wrong? Seems like a conservation of energy problem. And you get a cooler roof so less airco demand too!

Ah, unless you refer to shifting the release of heat from inside to outside earlier in the day?