You have a great truck,
The Unloaded weight the salesman likely pointed to is useless.
The unloaded weight is the number from when it rolled off the factory floor, no batteries, Propane tanks or fuel, and empty tanks along with no dealer installed options. The trailer will never weigh that again.
In short the trailer will weight at least a couple hundred pounds more than that before you ever see it.
To get to useful numbers do you know your trucks cargo or payload capacity? Tow Capacity? and how many people and gear do you intend to carry in it?
Then what is the GVWR of the trailer?
With those numbers we can get to how your load should work out.
The truck numbers can be found on the door pillar, the trailers on the brochure from Forest River for the model you are looking at.
add on; If you are looking at the Rockwood 2707 your loaded weight is about 8600, and the likely weight you would be pulling will be around 8000 to 8500.
At that weight your tongue weight should be around 1200.
If your truck can tow 10'500 you should be good on that weight, the cargo cap though will start with the 1200 tongue weight, add for all vehicle occupants ????? Gear/toys in the truck ????? are you still under the cargo capacity of the truck?