I always felt the Alethi were presented int he books as more middle-eastern/Indian than east-asian. However, due to Shallan's descriptions in the books, I've understood the Vedens to be much more caucasian.
She is literally described as pale-skinned, freckled, and with red hair. But i'm supposed to think she looks Asian? I call BS on that.
I've also always gone back and forth on the people from Iri, Rira, and the Reshi Isles. So many of them are blonde with tan skin.
And the end of the day, the exact race of each people isn't the MOST important thing to me. I do hope any adaptation doesn't present roshar as a modern day American city. You're supposed to notice someone is specifically Makabaki or from Vedenar, or Thaylenah. That's such an important part to the worldbuilding, and I know Brandon has specifically mentioned that. You may see more mixed near certain borders, but the various cultures stay fairly segregated. That is, aside from Bridge 4, apparently.