Hello Roach and welcome from Virginia.
I ride an R3Touring, which by Triumph standards is built for long rides. And I agree with that idea as I have had several 10-12 hour das in the saddle. A full tank of gas will get you about 2 hours between tanks at 85MPH.
With that said, any pre-2020 Rocket can be made for touring. There are many bags out there and windshields that work on the beast. (The 2020 models are no longer cruisers but instead Speed Triples on Steroids as per the factory).
Ask if the update kit has been installed on the older bikes. If not, you may have a not of trouble when second gear goes.