Remember shrinkage and settlement are two different things. The wood will shrink, the building may or may not settle that amount. In handscribed log walls there is another thing causing settlement, the cope spreads and the edges of the cope compress. That is not the case with D logs, the bearing is wider, essentially flat on flat. If a log checks, the wood has indeed shrunk but the overall height of the log may not change, the shrinkage dimensional change is largely in the check. There are a number of construction details that can prevent a log wall from settling from log to log fasteners, solid window and door bucks to the caulk and nails in the trims.
Is the gable wall solid log all the way to the peak or is it the more typical 8' of solid logs and log siding in the gable? If the latter there is no appreciable settlement above the 8' level. Next, how old is it? if more than a few year old it has done the majority of shrinking and then whatever settling it will do. Look around the patio door trim. How much has the wall dropped in relation to the trim?
I've done porches similar to this on log home kits with no callbacks. Those homes went through initial drying and settlement after the porch was built, and yet it has worked without putting in post adjusters or anything special. This house has more than likely already dropped about all it is going to.
That said, trying to match an existing roof plane rarely produces a sweet flat plane. I would do something though, the splash off that deck is going to do in the lower courses of logs on that house.