How do the characters in Dessa Rose show examples of stereotyping?
Although it is written as a "genre" book -- that is, a book written in the style of the old slave narratives -- Dessa Rose takes pains to either avoid or satirize stereotypes. For example, while protagonist Odessa Rose is an undereducated black female slave, she is also strong-willed and focused on her situation, instead of passively accepting it until a white person motivates her (a classic trope of slave narratives).
A stereotype that is embraced for purpose of realism is the dialect of the time. Slaves were undereducated in order to keep them from fomenting rebellious thoughts, and Dessa speaks as they would:
"And all what mammy say, what Aunt Lefonia and Mamma Hattie say, don't make Masa no ne' mind. 'Tarver known fo makin big babies on lil gals,' Masa say and laugh."
(Williams, Dessa Rose, Google Books)
In this manner, the stereotype of slave dialect is used to show both the deliberate undereducation of slaves, and the fact that slaves were as capable of rational thought as anyone else, even if discouraged by society.
A stereotype played entirely straight is Boss Smith, the plantation owner, who has little character beyond whipping his slaves; he perfectly fits the stereotype of the fat, brutal slave-master who sees slaves as subhuman.