Answer:
The characters speak in dialect to reflect the historical setting.
Step-by-step explanation:
The difference between the language used by the narrator and the language used by the characters is that the characters speak in dialect to reflect the historical setting. The dialogue provided from the novel is reflective of a 'southern', but 'uneducated' dialect, and this is further supported as the setting of Roll of Thunder, Hear My Cry is Great Depression-era Mississippi.
If you were to travel back in time to 1933, Mississippi, you would be able to find people speaking in the same dialect as the characters do here.