Years ago I had to do some structural roof repair on a '93 Northstar TC-800. I had to lock the lift mechanism in place while unfastening them from the roof. It was one of the smaller NS pop-ups with no AC.
I never had a reason to weigh it, but I will tell you that those roofs (albeit bulky) are pretty darn HEAVY.
Mine had the E-W bed over the 8' body so I am guessing it was an area of about 7'x12'. If I had to hazard a guess I would say it was every bit of 100# and 'prolly more. I do not think it was more than 200#.
It was a bear of a job and I would not attempt it again (I would buy one in better roof structural condition.)