It is, in large part, thanks to Tobe that the character of Miss Emily earns her symbolic "rose." Tobe's loyalty and dedication to Emily until her death infuses in her character a sense of worthiness, and helps her preserve her dignity despite of the fact that the town questioned a lot about her personality.
These are some of the reasons why Tobe, who is Miss Emily's manservant, is essential to the story "A Rose for Emily." While much has been written about the relationship between Emily and Tobe, the facts about his importance to the story that are most obvious are the following:
1. He was the liaison between Emily and the outside world.
Notice that, as a manservant, it is only Tobe who would open the door to the household each time the people of Jefferson, namely the Board of Aldermen, would attempt to cross the threshold that is the gothic, crumbling old mansion where Emily resides.
Tobe would have also been the person responsible for announcing the death of Miss Emily's father to the townsfolk. After all, Emily's only relations were all the way in Alabama, and she had no friends in town. Could it be that Tobe also requested help to get the body of Emily's father, since she was unwilling to give it up? Was Tobe in any way responsible for luring Homer Barron into the house?
2. He was the only person who was loyal to Emily.
There is something to be said to whoever wishes to typecast Emily's character. She is not entirely a loner, or entirely alone. She is not entirely unsupported, nor uncared for. This is because Tobe is there. Moreover, he was always there and remained there until the day that Emily died. He kept every one of her secrets, which helped her preserve some degree of dignity. It was his loyalty and his silence, despite of all that he knew, that helped Emily to continuously appear enigmatic and interesting to everyone. This is what built a lot of her legend in Jefferson. Tobe was instrumental in enabling and preserving that, thanks to his silence and loyalty.
3. His silence shows respect for Emily.
Had Tobe chosen to speak up and tell everyone what was going on in the house, Emily's entire story would have been quite different. The townsfolk would have never had the time to connect with her at the psychological level that they did. After all, a story about "a crazy lady" would have been easier to take in than the exploration of who she really is, and what made her act the way that she did. These latter actions are the ones that drive the town to still hold respect for Emily, and Tobe is to take credit for this.
Also, had Tobe decided to tell on Emily, her story would have been a tale of morbidity, debauchery, and insanity. Thanks to Toby, Emily, figuratively, earns her memorial "rose."
Other things are telling about Tobe. He ran away from town after Emily's death, likely because he knew what was coming.
The following passage is quite telling:
And so [Emily] died. Fell ill in the house filled with dust and shadows, with only a doddering Negro man to wait on her. We did not even know she was sick; we had long since given up trying to get any information from the Negro. He talked to no one, probably not even to her [this is what the town assumed], for his voice had grown harsh and rusty, as if from disuse.
From this excerpt, we gather that Tobe concedes nothing. We cannot quite ascertain what relationship he and Emily have, but definitely he keeps silence. Moreover, after Emily dies, he knows that "the big secret" will likely be discovered. ...
THE NEGRO met the first of the ladies at the front door and let them in, with their hushed, sibilant voices and their quick, curious glances, and then he disappeared. He walked right through the house and out the back and was not seen again.
Tobe remains loyal until the end and, rather than offering excuses or giving explanations, he majestically opens the doors to the household one last time, and does his job once more before going away forever. If any stories ever surfaced, or any conjectures were ever made about Emily, none of them came from the man who may have known her the most.
Therefore, Tobe is essential to the story for what he REFUSED to say and do, and for helping to preserve the legendary persona of Emily Grierson.