In William Faulkner's story, "A Rose for Emily," I would imagine that labels placed on characters in terms of protagonist, antagonist and hero are somewhat subjective.
In terms of the protagonist, this is usually the main character. We would also prefer to label such a person as the "good guy" as well, but in this case, we certainly cannot. (This is similar to Shakespeare's Macbeth. Macbeth is the protagonist—starts out as a hero—but he becomes a cold-blooded murderer as well.)
We can find plenty of antagonists in the story: Emily's father, Homer Baron, the town of Jefferson, and Miss Emily herself—in an odd way because she is the protagonist and the "bad" guy. (How to categorize her...???) However, Faulkner provides us with a complex character in Emily who cannot be easily explained away.
Setting aside the concept of antagonist and protagonist, there are certain aspects of Emily's character that make her seem "heroic" under her circumstances. She defies her father in a community of the South where women had no rights and were treated like possessions. When her father dies, she defies society first by sending her female relatives who come to stay, now that Miss Emily is unmarried and living alone, away. Then she continues to cause "tongues to wag" by going out with Homer Baron. However, even he can be seen in a negative light, much like Emily's father. In Homer's case, he is a "man's man," and seemingly not ready to give that up for Emily, though he also seems to be courting her at one point.
Emily goes through a time where she gives china painting lessons, perhaps bringing in some extra money. She defies the local representatives of the government who try to make her pay taxes: Colonel Sartoris did away with her need to pay taxes when her father died. Though the Colonel is long dead, Emily stands up to the gentlemen who come to collect the money, and dismisses them out of hand. Even when the smell appears at her home, the community takes care of it quietly and privately, until it goes away.
"Dammit, sir," Judge Stevens said, "will you accuse a lady to her face of smelling bad?"
In later years, Miss Emily becomes very private with only Tobe, her servant, as company. She is alone but defies any attempts by the community to alter her self-imposed isolation. With all of these conventions that she defies as "merely a genteel southern belle," Emily cannot be seen completely as a victim. She stands up to the two overbearing men in her life—her father, and then Homer (she really stands up to him), and ultimately becomes an independent woman when such a thing was socially unacceptable and unheard of.
In these ways, we can see Miss Emily as heroic. She defies society, takes care of herself, stands up for her rights, and does not allow anyone to tell her how to live. It is something heroic when a member of the "weaker sex" can stand up to a male-dominated society.
There is no other hero in the story. Heroes are often defined as those who are courageous and triumphant in the face of adversity, which Miss Emily is, but they are also self-sacrificing for the good of others: Miss Emily is not.
Perhaps we can agree that she is the story's protagonist, and that she has strong heroic traits for a woman of the time—and she has suffered at the hands of the men in her life. Perhaps we should agree she is deranged. She is a "dark hero" who manages to survive on her terms, who also murders a man and sleeps with his corpse. She defies a label.
There are no clear-cut heroes in "A Rose for Emily." Certainly, Emily is no hero, but perhaps Homer Barron comes closest to being one. Homer comes to town to supervise the construction of new sidewalks in Jefferson--a way to improve and modernize the town for all the people. Everyone he encounters becomes his friend, and he becomes the center of attention wherever he goes. His laughter is contagious, and he befriends the friendless Miss Emily, courts her and makes her happy--at least for a while. The reader is never told whether he made promises to Emily that he did not keep; perhaps Emily, in her possessive manner, refused to accept that their relationship was only a temporary one. But, long after Homer was able to apply his good-natured ways, he was still making Emily happy--keeping her company in the bedroom which no one else had visited for 40 years.