Buying First Home! Had it inspected! The inspecter said all was good!
It depends on how much the roof deflected in that spot. It could be a structural weakness for sure. If the truss below is damaged, it sould deflect along a good size area. I think perhaps the was a leak in the roof there that went unrepaired for too long. The sheathing could have water damage from prolonged exposure, and may be rotted in a small area. Often the wood will feel "spongy" if you can access it from the underside - and there will certainly be visible evidence of any water damage too. IF you can get to the underside of the roof sheathing I would definitely check this out, if only to rule it out.
It's hard to argue with the home inspector's assessment though. If it supported a man weighing 200 pounds, even though it "gave" a little, the roof structure is sound enough to pass inspection. And if the roof is new, and free of defects, then it will not continue to deteriorate (unless the water is coming from somewhere else - maybe from higher on the roof and running down to this spot). So it is "fine, " even if it is not in great condition.