Hi FailsafeOperator,
I don't personally have a carbon bike but plenty of others do and have used them over many miles & are happy with them so there's no reason to rule them out as lots of people have said above. I've not ridden either the Domane or Roubaix but you might be interested to see this Bikeradar video:-
http://www.bikeradar.com/road/gear/article/specialized-roubaix-vs-trek-domane-48103/
As some others have probably already mentioned there's no substitute for getting out there are trying a bike for yourself if it's possible to do so.
As you don't seem set on a specific frame material at this stage there's no need to rule any of them in or out because there are plenty of good options out there in all materials. As some have already suggested there are some lovely titanium options out there and available to you in the US if you fancy going for something a bit special.
However if you want some other options and want something a bit different from the big brans you could maybe consider some of the following:-
Bombtrack Bicycle Company (link follows)
http://bombtrack.com
Bombtrack make some lovely steel bikes if you look through their range. But if you want carbon they are also going to bring out a carbon version of their Tempest (hopefully the link to their Instagram account works below to show the carbon Tempest C ).
View: https://www.instagram.com/p/BaQ8nWhgnku/?hl=en
Breadwinner Cycles -
https://breadwinnercycles.com
You've said that you're interested in custom builds and do some lovely hand built custom bikes.
Mason Cycles (both Aluminium and Steel options) -
https://masoncycles.cc
I wasn't going to mention Mason Cycles (a British company) due to you being in the US. However having taken a look at their Instagram account there seem to be plenty of Mason bikes all over the world including in the US and so perhaps they do ship there so if you like their bikes there's no harm in contacting them to ask.
They've recently launched a second generation of their aluminium Definition model:-
https://masoncycles.cc/blog/road-cc-definition2
Or if the link above to the video interview about the Definition 2 doesn't work then try this:-
View: https://youtu.be/5pkGRELA2bQ
Reviews of the original Definition:-
http://road.cc/content/review/149005-mason-definition-road-bike
There's also the Steel Resolution:-
https://roadcyclinguk.com/gear/mason-cycles-resolution.html#sgyXemC0QEPQyR7O.97
http://road.cc/content/review/152814-mason-resolution-105-hydro
http://www.cyclingweekly.com/reviews/road-bikes/mason-resolution-ultegra-hydro
http://www.bikeradar.com/road/gear/...view-mason-resolution-ultegra-hydro-15-49680/
Or the aluminium Bokeh:-
http://www.cyclingweekly.com/reviews/adventure-road-bikes/mason-bokeh-ultegra-hydro-700c
http://www.bikeradar.com/road/gear/category/bikes/road/product/mason-bokeh-force-review-50957/
For me personally I'm a fan of steel and I have a 2016 Kona Roadhouse which I absolutely love but all bikes are different with different characteristics so you need to find the right one for you as what's right for one person isn't right for the next:-
View: https://youtu.be/ltLN1bOXS10
http://road.cc/content/review/182237-kona-roadhouse
https://www.bicycling.com/bikes-gea...-modern-road-bike-with-a-thirst-for-exploring
http://www.roadbikereview.com/cat/latest-bikes/road-bike/kona/roadhouse/prd_518029_5668crx.aspx
You might also see something of interest in either of the following links but you'd have to check which ones are available in the US if any are of interest.
http://road.cc/content/buyers-guide/230664-17-2018s-best-disc-brake-endurance-do-it-all-road-bikes
https://www.theguardian.com/lifeand...esis-datum-pickenflick-mason-resolution-jamis
Enjoy looking for bikes and getting out there to try as many as you can. Good luck finding the right bike for you!
John