That was a nice decription for construction of a framed trailer, but the Rockwood is laminated wall.
An aluminum perimeter frame with some stiffeners is set into a foam core that has had channels cut for the frame, and for routing in-wall wiring. Don't know about F-R, but some manufacturers put the wiring harness in the channels at this stage. Also in cutouts in the foam core will be the attachment plates, heavier plywood or sheet metal, for everything that will hang on the interior or exterior of the wall.
On this goes a precut interior panel the size of the whole wall, which has adhesive on it. Flipped over, a precut luan exterior panel the size of the whole wall, with adhesive is applied. What happens next depends on pressing technology at the plant.
If using mechanical presses, this luan-foam-luan sandwich gets pressed as the adhesive sets. Then the outer fiberglass skin, pre-cut and whole wall size, with adhesive, is layed on the sandwich and the wall gets pressed again.
If using vacuum bonding, the outer skin goes on before pressing, the whole thing goes in the bag at once, and pressed together for a longer time. Slower setting adhesives are used.
But either way, the entire surface of the interior and exterior panels is glued to that foam core. This sandwich is what gives the wall its basic strength, and it is meant to never come apart.
What happens when a wall like this gets wet inside is that the luan panel rots, its own two or three layers separate. Remnants of luan will be pretty well stuck to the foam. Because the adhesive is stronger than the foam, chances are pretty good that pulling off the interior panel where it is still solid, or cleaning remnants where it rotted, will tear up the foam core.
What happens in further manufacture varies. In some RVs, all the interior fixtures that will set on the floor are set on the floor. The laminated wall can be set on the floor, or it can be fastened to the edge of the floor frame (or if Winnebago, two metal channels interlock.
The ceiling and roof might be built up framed with rafters or trusses atop the walls, or the whole thing might be another sandwich panel (this is still pretty rare in low cost TTs). If coming as a single piece, the top might screw to the edges of the wall, the wall might screw to the edges of the roof structure, or interlocking metal channels might be used.
The result, for repair purposes, is that to repair a badly damage laminated panel wall, it is necessary to detach everything from the wall, including the roof, and remove the wall from the RV, replacing it with a newly built wall, or at least rebuild the wall as it was originally built on the bench, if you can do so without destroying the foam core.
This makes laminated walls so expensive to repair that a major delamination is often a total loss, even on a fairly new TT. It is not usually a DIY job because of the need for the specialized materials, tooling, workspace, and pressing equipment.
This is one reason some RV buyers prefer walls that are built up as frames, rather than laminated foam core panels. These are still not simple to repair, but repairs can be made.
If your roof-ceiling structure is not laminated, that is probably reparable. The section over the slideout, what has most likely happened is that the luan panel has come apart, and you might be able to make a cosmetic repair. I don't know that you can make a structural repair, to restore the original strength of that section over the slideout.
Whether or not you need to restore that strength, I also don't know. If you are lucky, most of that section might have aluminum framing, a header over the slide opening and some studs carrying the weight of the of the roof support channel down to the header. But this framing, if there, is primarily reinforcement of that narrow section over the large opening, because in a laminated panel, the main load carrying is done by the inner and outer skins, as they are bonded to the foam core. You will not regain that strength with a local patch, and you are not likely to duplicate the bond strength without pressing the wall.
I wish you good luck. As it is a small damaged area (or maybe I should say, if it really is just a small area that has come apart) you might have some probability of success, if you are careful in the future not to put to much weight on the roof over that slide opening.
Tom Test
Itasca Spirit 29B