Sort of depends on what you mean by "full service". Most any diesel shop can change oil & filters, check transmission fluid & filters, check air dryer, etc. But your chassis is an orphan (Roadmaster) so some shops may be reluctant to do much with it, maybe even a chassis lube. And your generator probably should be serviced too.
Some Freightliner dealer service centers aren't interested in non-FTL business ( ditto for Cat dealers), but it's worth a call to ask because they are generally reliable. You shouldn't have that problem at
Cummins Coach Care locations, plus you can get usually Onan generator service too. Coach Care shops also do some of the more common RV "house" services too, e.g. appliances, LP system, etc.