Welcome to Mississippi, circa 1933. Bad news: We're stuck squarely in the era of the American South's segregation and Jim Crow laws. We're hanging out with these characters before the Civil Rights movement. Way before. So, issues relating to race are a major concern in this novel.
Roll of Thunder, Hear My Cry shows us the many injustices inflicted upon blacks by the white ruling class. But, Taylor also provides some examples of non-racist whites, as well. Big Picture Alert: The novel shows how a major part of living as a black person in this time and place was learning how to navigate the unfair system without having it crush you and your dignity.
Papa is right: Stacey and Jeremy can never be true friends because their different races set them too far apart.
Stacey's and Mama's actions against racism in the novel are quite similar to the civil disobedience of the Civil Rights movement.