I've got some of the Wolf Boxes (
frogsisland4x4 - Home and others).
They are sturdy and stackable but pricy and don't seal completely so you'ld probably need to stow your kit in dust/waterproof bags inside the boxes. I'm not sure they can be securely locked either (I haven't tried to be honest).
By the time you add the cost of liners and the weight of the boxes on the roof I would have thought waterproof stow bags would be a better option.
Maybe a couple of boxes for sharp, heavy items inside the vehicle rather than on the roof?
Just my opinion...