I had difficulty lifting the roof in a demonstrator, so bought the speaker-stand crank device even before I took delivery. It does work just fine. But it is a bit of a bother to carry and use, so started trying various techniques to lift the roof unassisted. I don't have a rack or carry stuff on top.
I can't describe my method exactly, plus you'll do better to figure out what works best for you, but I'll give some hints. I sit down on the sofa to raise the rear, pushing up on the ceiling board, and at the same time pushing back on the hinged lifting panels. You're not supposed to lift just by pushing on the panels, but they are strong and if you push up with one hand and back on the panels with the other as you stand up, it goes up without excessive effort. Just remember to put the strap around the knob once it pops into place or the back will fall when you try to lift the front.
To lift the front, I remove the cushion above the water tank. Crouching I stand on the cabinet above the tank, place my shoulder against the lifting board, and stand up, lifting with my shoulder. That uses the muscles in my legs which are stronger than my arms.
And of course leave the door open when lifting so air can flow easily into the camper as the roof goes up.
Hope this helps.