Just so happens I looked at a friends RV the other day (Minnie Winnie) and his storage compartment. If you get a roll up around 10.5 feet in length (max) and under 100 pounds you could do it. His had the main side door opening approx 24"x36" and a separate entrance of 24"x24" from the rear where one could grab the boat from a diff angle and move it around. We used to put the 12.5 foot Zodiacs in the back seat of Ford Torino and LTD's.
That was my plan, but FWIW I have a 42" wide bay in my Vectra and the boat / transom is just a bit wider than that on my 11' when in the bag on my Mercury 340 air deck. So now the bag rides on the sofa while under way.