I don't have solar (yet). Maybe a year or so. But solar panels work better when the are cool (ironic because you need the sunlight which is what gets them hot -)).
So what if you put Styrofoam underneath the panel. This will keep the reflected heat from the roof off the panel. Now the question is (1) will this help at all (2) should the foam be left white or black.
Are you in the position to try this experiment. My belief is that black is the better choice.
Is this a waste of time, IDK. I don't think so. If you look at the specification of your panel you'll see how quickly the efficiency drops off as the temperature of the panel goes up. At high temperatures: 80F-90F it falls off like a rock.
So if you can keep it below the 80F and down in the 70s, this might be a cheap fix.