Toad Roof Rack Mounts?

Yakima and other roof rack companies offer some generic kits, as well as vehicle-specific kits. The traditional approach, as I understand it, would be to attach a set of rails to the roof fore-and-aft, and then clamp legs to the rails where needed, and the crossbars or whatever to the legs. There often are also fixed leg mounts available.

Here's Yakima's intro page on custom installations.