I spend about 25% of the year in Midland, a little east of Mt. Pleasant (the other 75% in Denver area). I have a Roubaix with 32’s and it rides well on the rough farm roads and most area gravel roads. Thinking about getting a MTB for here also but don’t know the trails well yet. I think you’re Domane will be a great all around bike for this area.

If you happen to bring your MTB check out DTE trail in Chelsea, one of the best in the state. Its probably a 1.5-2 hour drive for you though.

I'm from SE Michigan, and just did a 4 day, 400 mile ride up the West coast (St. Joseph to Petoskey) this past week. I'm not super familiar with cycling in Mid-Michigan, but can say generally speaking that our roads are generally in rough shape, mostly due to them not lasting due to salt being used during the Winter. We're a bit behind the curve as far as being "cycle-friendly," but there are bike trails popping up all over, and dedicated bike lanes are beginning to become a "thing," which is good.

I'd think you'd have no problem finding places to ride the MTB, but the road bike would take a little bit of research to find decent routes. The bigger tires on your road bike should be plenty for the rough roads, though, so I'd imagine either bike would give you lots of hours of great riding, whichever you choose.