Rosie Roberts reveals that she has killed the son of the merchant prince in Edgar Lee Masters’s Spoon River Anthology. Rosie is a prostitute at Madam Lou’s, and the merchant’s son is one of her customers. Based on his reaction to learning that following her appointment with him, she is planning to meet her lover, it appears that the merchant prince’s son may have fallen in love with Rosie. The merchant prince’s son has offered her a large sum of money to stay with him, but he is angered when she says that his money does not matter and that she intends to meet the man she loves that night. In his anger, he pushes her down. She responds by shooting the merchant prince’s son.

The story is hushed up to avoid scandal, and the wealthy merchant bribes the newspaper to report that his son died while cleaning his gun. Rosie believes the false story has been printed in exchange for the merchant spending a considerable amount of money buying advertising from the newspaper. She also seems to believe that the “crooked police” have helped cover up the truth of the man’s death. Rosie says she has written a letter to the police, confessing the crime and revealing her whereabouts so they can arrest her.

"The merchant prince," as the previous educator noted, appears to be a powerful business owner with influence over the local newspapers, due to "the bribe of advertising."

What is interesting about the poem is that Rosie—who, as a prostitute, would epitomize immorality for some people—establishes herself as righteous while the institutions that we trust—the police and the newspapers—are "crooked" and accept money to avoid the truth. The truth is that Rosie "killed the son / Of the merchant prince . . . Because he knocked me down when I said / That, in spite of all the money he had, / I'd see my lover that night." The murder was an act of self-defense.

Though Rosie is a prostitute, she still maintained a "lover." Her assertion of a private life, which included love, disrupts the expectation that prostitutes only care to make money. The merchant prince made the mistake of believing that he could control and possess Rosie with his wealth.

The poem illustrates an interesting reversal of power; a prostitute becomes a moral exemplar who exposes the corrupting power that money had over the people of Peoria, Illinois—all of them, that is, except for her.

Each of the poems in Edgar Lee Masters' Spoon River Anthology is told from the perspective of a ghost.  The ghosts, former residents of the small, fictional town of Spoon River, reveal much about themselves, their intersecting lives, and their views on mortality.  "Rosie Roberts" is no exception.

When reading poems in this book, it is helpful to remember that they are written in a very limited first-person point of view.  Many details are left out, but can be extrapolated from the information given by the ghost.

Rosie was formerly a prostitute in the large city of Peoria, Illinois. We can figure this out by noting that she is addressing the police of Peoria from her "girlhood home in Spoon River," and that she mentions "Madame Lou's" twice (brothels are operated by madames).  She confesses to killing "the son/Of the merchant prince," a crime which was then covered up by "the crooked police" to avoid a scandal.  If we know that she was prostituting herself in a large city at the turn of the century, we can guess that the "merchant prince" is probably some important businessman.  In order to keep his son's visit to a brothel out of the papers, the businessman asked the police to report the death as an accident.

Very sick and on her deathbed, Rosie obviously wants to repent for her past and face up to her sins.  This is why she has chosen to write to the police and confess her crime.  We can see that, despite the fact that she was a prostitute, Rosie does retain some morality, and, in fact, could be considered more moral and upstanding than the police or the "merchant prince."