casting 101
Read how the characters are described, then find actors who fit the part. Done.
shareAre you suggesting you should cast actors solely based on their resemblance to the characters ? Cause that has been done in the past with other Franchises ( Ex. James bond) and it backfired, cause first you need to make sure the person can ACT the part, Elba could still suck in the role and he I know he doesn't look like Roland at all.
But he could still pull off the character's personality and actions, so well that it won't matter how he looks.