Usefulness of a roof rack?

Greetings gentlemen, 

When i travel with my Jimny, I use Thule squarebars mounted to the factory rails. i carry a Thule roofbox with lightweight camping gear.

I like the direct bolt to roof, racks. Such as the one offered by Horntools. But my question to people with aftermarket racks, can you mount a roofbox to them, or crossbars if need be?

Thanks!

Hi
Isn't this going to depend upon the shape of the selected rack and the size of the roof box?
I have a Jimnybits expedition rack and I use it predominantly to store any wet camping gear when I break camp. I put it in stuff sacks and throw it on the top as it has cross rails to keep any items off the roof.
It would be possible to fit a small roof box within the frame sides on the cross rails, but the wind deflector on the front would prevent a large box being installed. 
So it's a yes to cross rails, maybe to small box for the Jimnybits offering. Great if you are happy with things in bags!

I use the large Horntools one. It has a railing and therefore it depends on the box you want to mount. I did mount my box for skies, I just attached them to the front an back of the railing.

There are some drivers that removed the railing with a grinder. Quiet easy because the rack is made of aluminum. And then any box would fit.

Generally the roof rack makes a very stable impression and not too much noise on the highway.

I have cross bars the same as Lambert. I mainly use them for long things that won't fit in the car, like lengths of timber and kayaks, but I've also considered a roof box to put bulky but light stuff in (like the massive duvet my girfriend insists we take when camping). It seems to me that the big roof rack/cages are less useful than traditional bars for most of the things you're likely to want to carry on the roof. They also eat into the precious 30kg load limit and add height. But I believe they are and important part of "the look" if that matters to you.