I think we should also consider Faulkner's own sympathy for the character that he has created. We offer a rose to someone as a display of love or affection, and clearly Faulkner wants us not to despise Miss Emily but to understand her. We are given a character who has committed a terrible crime, the crime of murder, and who has been known for her superior attitude, disregard for authority, and utter disrespect for her fellow community members, but she is still not someone who we want to hate. We want to pity her, instead. We understand why she did what she did and, even if we cannot excuse it, we cannot condemn her either. The rose acts as a peace offering to a woman who has been controlled by her father, scorned by the town in which she lived, talked about behind her back, and never given any of the help that she might have needed to avoid ending up in the situation that she ultimately ended up in.
William Faulkner's title definitely connects with the theme of the story. If you think about it, imagine circumstances when people are given roses. Usually, it is a formal occasion where the rose is given to symbolize honor, respect, affection, or to make the person feel special or acknowledged. Also, roses are a noble flower, the top of the line in elegance and beauty.
Now, keep that in mind as I describe the next scenario. Emily's family came from a time where their wealth and name meant nobility and earned respect from the townspeople. They were like the royalty of the town; they were the top of the line. People revered them, and their wealth and position bought them special privileges. They recieved tributes and honor from their position. All of this ties to the rose--when WE meet Emily, that honor, respect and royalty has faded away, and all that is left is the crumbling remains of the legacy that was once her family. No longer does she get the "rose of respect" or tokens of honor and affection from the town.
Faulkner uses the rose in the title to symbolize the decline of Emily's status; the story is a tribute to her faded legacy. It is her last hurrah, a last record of the last of a dying family wealth and reputation. The last rose offered on her behalf. I hope that those thoughts helped; good luck!