The world map for Roshar changed dramatically between various iterations of the book.
Work on this novel started when I was fifteen. Back then, most of the plots and characters were combined with another world of mine, called Yolen. (That's where the book Dragonsteel takes place.) Somewhere in my early 20s, after I had a whole lot more experience and knew (kind of) what I was doing, I realized that the plots I had going in this world didn't click well together, so I divided the books into two separate series.
I wrote Dragonsteel first, back in 1999 or 2000. (Although Dragonsteel was the third book I wrote in the cosmere—after White Sand and Elantris—it was meant to be the chronological origin of the sequence. Hoid was one of the main characters of that series. The first book even includes significant viewpoints from him.)
I started outlining The Way of Kings fairly soon after. That original map I imagined as a continent with three prongs facing downward, with a connection at the top. There was the Alethi prong in the center, Shinovar to the west, and a long prong with Natanatan on the east.
Over the years, my worldbuilding skills grew. And part of that growth was realizing that the map I'd designed didn't work well for the story I wanted to tell. I wanted something better, and I changed designs.
I gave Isaac the outline of this world that became Roshar. (Based on an iteration of a Julia set, though for a while I played around with making the whole continent a cymatic shape.) That didn't happen for Mistborn, where I basically just told him, "Make the world map as you wish, with these guidelines." Mistborn, I knew, was going to happen basically in a couple of cities.
The Way of Kings was going to be huge, and I wanted scope for the project. That meant a big, epic map. I'm very pleased with Isaac's work here. Do note that this is a southern hemisphere continent, with the equator up north.