I would never use a RV dealer to buy and mount tires on any trailer...or wheel barrow.
Most tire stores in suburbia aren't set up for a vehicle pulling a trailer nor do they have enough trailering customers to offer good advise.
When I was pulling for a living I did all my trailers tire service with mostly Goodyear truck tire stores. They know a hell of a lot more about best tires for a trailer than the type stores I mentioned above. Plus they have enough room and proper equipment for servicing trailers.
Both small towns near me (10k -20k population) have 2-3 tire stores each and do all the truck and trailer service in their area. Drive by anytime and their mounting tires on some type of trailer.
You can always buy tires of your choice off the net (tirerack.com or many others) and let a area tire dealer that has the equipment mount them for you.