As much as we do not want them, a good quality set of roof bars to hold a basket, flat rack or pod (if that’s what you’re into), is an absolute must for touring.
You really need to look at the specific loads that can be carried and be able to trust the people installing the system. You would be surprised the amount of weight people normally strap to the top of their vehicles.
That said, it is still best to only strap down light equipment to the roof. Things like swags and mattresses work best here.