I'm running a goose, so hitch overhead clearance is not an issue. The toolbox sits below the rails, so also will clear fine. I've considered the roll-ups. Is yours one that is like a roll-up garage door w/ a box it retracts into? If so, how large is the box. By what you wrote, I'm guessing it is only about 6 inches wide from the headwall. My brother had a similar roll top, of what brand I'm not sure, but the box was 10-12 inches from my recollection. That would waste way too much space in front of the toolbox. Does your roll-top leak or do the rails contain and drain the water?

Thanks