This series seems near impossible to pull off effectively on film, but I am still interested to see how it turns out.
As for the racial tensions, it's been 8 years or so since I finished the series, but I think Roland was just as confounded by Eddie as he was Detta/Odetta. I don't think it would have to be centered on their racial differences, but simply that they are from different worlds. If anything, I remember more racial tension between her and Eddie, and that can still be played out with this adaptation.