sorry, I didn't mean to mislead you, there is aluminum tube framing for the floor and walls that have the aluminum tubing spaced out. When we were shown the cross section samples for the roof, floor and walls each sample had part of the aluminum tubing in it. The roof does not
have aluminum trusses every so many inches.
I called Forrest River and inquired about the Roo's roof construction. The roof has the membrane, 1/4" luan, 4" thick foam (with built in ducting, at least for my model which is the 23ss) and 1/4" luan, it is crowned and the whole roof is vaccum bonded. There is an aluminum truss on each end of the roof and one down the center of where the air conditioning unit is located, the roof has 1x2 aluminum tube framing the perimeter.
I asked about installing a permanently attatched solar panel system to the roof and he said that the safest place to mount the solar panel mounting brackets would be along the edge where the aluminum framing would be and that there would be really nothing of substance to grab onto in other parts of the roof. He also mentioned that it would be best if you didn't have to penetrate the roof membrane.
The first forrest River person I talked to gave me a name and number to call which could provide you with information on things like dimensions for the aluminum framing, which might help you figure out the location of the aluminum tube framing or other parts of the trailer. The Forrest River Customer Service person to contact is Mark Akins, his phone number is 574-642-0368, I was told that he should be able to direct you to the correct department for information that you may need. I have actually talked to Mark before concerning the 2nd year extended warranty, to inquire about what is actually covered. He was very helpful and gave me the name and number I needed to get the information I needed. All of the people who I have contacted at Forrest River so far have been very helpful.
I hope this helps you, Good Luck with your project.