While using the refrigerator vent is a popular route, there may be better locations to route the wiring, provided you can bring yourself to drill holes through the roof.
If I were to do this on my rig, I'd drill a hole just forward of the Grey tank stack vent, which actually goes up through the interior wall on the passenger side. Of course, you coach will likely be a bit different.
I would highly recommend a borescope type of camera (you can buy them on eBay for less than $20), if you are considering doing this so you can properly locate the intended path of the wiring before drilling any holes.
The biggest issue I see though is adequate support on the roof for the solar panels. It is not so much supporting the weight, but having adequate support for the mounting screws and brackets.
The roof is constructed with aluminum frame members with a very thin covering of luan plywood. The drawing I have says my roof is sheathed with 2.7mm luan - which is less than 1/8" thick.
If you drill the solar panel supports into that thin of plywood, they most likely won't provide enough holding power, and the screws will easily rip out.
Even if you could adequately bolt down the supports, I'd be concerned about roof flexing caused by lack of support as you drive down the road.
In contrast, Thor uses steel backing plates for everything that is attached to the roof. Unfortunately, the only steel plates on the roof Thor added for customer gear on some models is for a satellite antenna.
So, you really have to drill into the aluminum frames to bolt the panels down, and provide adequate support for the solar panel.
I would recommend asking Thor for a set of roof prints so you know where the aluminum frame members are located. They sent me a set for my coach for the asking.
You may also find that you may have to add some metal sheathing or blocking to the top of the roof to have adequate mounting locations, especially if you cannot line up the solar panels to aluminum frame members.
The only thing that works on a RV is the owner...