Solar panels should be installed at fairly steep angles to be effective on roofs. In fact, in northern areas they may need to be sun tracking. 30degrees off perpendicular drops the out put to 70%. so all this increases roof snow load.
There is also an issue that these need to be cleaned frequently.
I saw one roof yesterday that hsd three rows of pannels, spaced and at raised angle. That will collect snow.
So now what is the snow load plus dead load? was 1 Kpa, but now perhaps 2.5 plus panels. Expect deflections, if not failures.