Why doesn't Mrs. Jones want to embarrass Roger?
It is very clear to Mrs. Jones that Roger is besides himself with shame and embarrassment. His silence when she grabs a hold of him reflects this. She recognizes almost immediately that there is no need to embarrass him for he already feels shame as to what he has done.
This might be where her response to a young kid's poor decision is so powerfully compelling. She recognizes Roger did a stupid thing. Yet, she does not use her position of power over him to berate him or belittle him to a point where he feels less of a human being. She does not want to embarrass him because Mrs. Jones realizes that this will further alienate him. Mrs. Jones understands that young people sometimes make poor choices. This becomes where she becomes a nurturing figure for Roger. She does not use her position of power to embarrass him because that is not going to fulfill her hopes that Roger do the right thing in the future. In treating him with dignity, she recognizes that she, too, has done things in her past of which she is not proud. She wishes Roger to avoid these same mistakes, something that can be better accomplished by not embarrassing him and seeking to exert power over him.