The roof on my RockWood TT was crowned,(well, it was until a large metal beam flattened it out
) not sure if they all are but I would imagine most are.
To support the AC unit sounds like it would require some structural mods, may have to remove paneling inside and cut into styro to add bracing. Otherwise it will probably only get worse. I wonder if this unit had previous damage? Does not make any sense for water to be pooling around AC unit, if this was to happen in ANY RV you would have leaks everywhere as the AC unit is just held on by a few bolts that kind of sandwiches the roof material between upper pan and lower fascia/control panel, not at all a hermetically sealed joint.