Unless your married to the Good Sam routing app, which I've not used, you could try the RV Life Trip Wizard
that is created by the sponsor of this web site. I used it to plan a month long trip from SW Idaho to Key West and back. There is a web based tool that is more handy than the smart phone based app.
They used to have a 30 day trial, so you've got nothing to loose by having a look. The only disappointment for the routes, is that they don't cleanly export to something you can import into a GARMIN GPS. Or to be more accurate, for me it wasn't a slam dunk transfer to GARMIN base camp to allow it to be imported into my RV GPS without making a lot of changes .
Perhaps there is a Good Sam routing wizard amongst the group.