I would agree that Miss Emily was the rose. She lived her life in a patriarchal society, and Faulkner makes it clear that any chance she had at continuing to bloom in a fulfilling relationship was ruined by her father. He held any interested suitors at bay until they simply stopped coming, and the bloom was long off the "rose" after Miss Emily's father died.
In response to post #4, I don't think the Negro is her rose. While he is her constant companion, it is probably more from a sense of fear that keeps him tied to Miss Emily. He must know about Homer's dead body, but as a black man in the post-Civil War South, he knows that the murder could easily be blamed on him, and he is between a rock and a hard place -- come forward and be blamed or hide it and be blamed for hiding it. He literally makes a run out the back door at the his first opportunity in 40 years.
Miss Emily is the rose. She is the "flower" of the south, but not without her thorns. Telling the story is the final tipping of the hats of all the men to Miss Emily and all she stood for--the Old South, the rituals, the unspoken rules (many which still exist today), and perhaps her final victory over the pushy North as embodied by Homer Baron whom she prevented from ruining her reputation.
The rose is a symbol, which is when an object or person or action, etc., represents something beyond its literal meaning. There has been much speculation about what the "rose" really is. My own opinion is that the rose represents the narrator's own tribute to Miss Emily by telling her story. The narrator of the story does not judge Miss Emily at all when he or she tells her story. He relays what happens with a smattering of the town gossip about her; however, he does not pass judgment on her and the reader can sense that perhaps the narrator feels sorry for Miss Emily because of her very difficult upbringing and environment.
Maybe the "Negro" is Miss Emily's "rose". He is the only constant in her life, and through him she was able to hold on to some companionship. This man never turned his back on her, even when she was a "pauper". He did not leave her until she left this world.