I think that the perspective changes if Roger is elevated to the first person because the focus of the entire narrative is lost. Where the short story is powerful is this transferal between the old and the young, where struggle is understood by the latter as a result of what the former endured. It is not about how the young understand the old, but rather how the process of pain and struggle is something universal, experienced by both age groups. We know that Mrs. Jones had struggled in the past. We know that her life was not easy. We know this, and yet we do not know the exact implications of it. It is here where the power is revealed. Hughes leaves it up to us to figure out what she endured and whatever it is, this lesson is passed on to Roger. If we are clouded with Roger's perceptions, it makes the story about him, and not about the universal nature of struggle that can be appreciated by old and young. Roger is a part of this dialectic, but becomes it if he is elevated to the first person status. Additionally, the ending gains so much more if we are left wondering what Roger felt when the door closed behind him, being unable to thank Mrs. Jones for what she did for him. If he is speaking, that mystery is gone. In this the perspective and the significance brought out without first person narration is lost if it were to appear in the story.