I have a 2014 Laramie 4X2 with the new EcoDiesel and it is a real nice truck.
Saturday 7/19 I pulled a new to me 2005 Rockwood Roo 21ss from SC to GA for some 170 miles, it was 40% country road and 60% highway, raining the entire time and about 75f and all hills. I have about 30+ miles of very long grades, and the truck had plenty of power. I was passing people in the left lane without any issue.
Below you can see my set up and a picture of my fuel stats.
If anyone has any questions, feel free to PM me.
Also, I need a owners manual on a 2006 Roo 21ss if anyone has one or could point me to an online resource.