"A Rose for Emily" is set during the early 20th century, and segregation and Jim Crow laws were the rule of the white-dominated Deep South. Faulkner's Jefferson, Mississippi was no exception. African Americans were usually treated as second-class citizens--servants to, but not equal to, the whites of Jefferson.
Colonel Sartoris, the mayor--he who fathered the edict that no Negro woman should appear on the streets without an apron...
The "N" word is used matter-of-factly by the omniscient narrator (presumably a citizen of Jefferson) to identify African American laborers who worked under Homer, who liked to
... cuss the niggers, and the niggers singing in time to the rise and fall of picks...
Miss Emily's manservant, Tobe, receives somewhat preferred treatment, perhaps because of his position with the Griersons. He is rarely referred to by name, but usually as "the Negro man." Faulkner barely touches upon the subject of racial relations in the story, but it is clear that African Americans are at the bottom of the Jefferson social order--no longer enslaved but not yet equal.
The white townspeople treated the African Americans that lived in Jefferson much like the slaves were treated. Miss. Emily had an African American servant who took care of her.