So, the gist of it is - solar panels 'reflect' heat better than your average rooftop. And during the night that rooftop is not as hot so it does not heat the surrounding area.
This is kinda the desired effect. Paint rooftops white and you will have even better heat radiation. This is already being done in hot countries. And they are developing paints that do that job even better.
If houses don't heat up during the day then they don't need that much air-con.
Basically this heating up from solar panels is outweighed by other benefits.