Roderigo is a Venetian desperately desiring, but a rejected suitor of Desdemona. He becomes Iago's pawn, wounds and is wounded by Cassio in an unsuccessful attempt to murder the lieutenant, and is killed by Iago.

Roderigo is identified in the Dramatis Personae as a gull, a dupe or easy mark. Roderigo is gullible; he believes everything Iago tells him and does everything Iago commands of him. At the beginning of the play, at Iago's instigation, he alarms Brabantio with the news that Desdemona has eloped with the Moor. He sails with Iago to Cyprus and, while there, serves as a pawn in Iago's plan to destroy Othello and Cassio. Upon instruction, he picks a fight with Cassio when the latter keeps watch during the general celebration. Later, he attacks Cassio in the dark and wounds him, suffering a wound himself. Roderigo has given Iago money to negotiate with Desdemona on his behalf and thinks that the tasks Iago assigns him are intended only to remove Cassio from the picture, paving Roderigo's way to possessing Desdemona. Although his actions are despicable, he does evoke a measure of sympathy in the way that he is so utterly manipulated and ultimately betrayed by Iago, who stabs the wounded Roderigo on the dark street in order that he might not reveal Iago's involvement in Cassio's wounding.

Roderigo is continually threatening to quit his pursuit of Desdemona and cease giving Iago money for his intervention in that matter. Each time he does so, Iago assures him that Desdemona's attraction to Othello is only physical and that she will tire of the Moor fairly quickly. Iago suggests that Roderigo's best course of action is to accumulate a solid financial foundation. Iago tells Roderigo over and over to "Put money in thy purse" (I.iii.341-360), implying that, when Desdemona has satisfied her sexual lust, she will be attracted to the rich and stable sort of man. At one point, in his frustration at not realizing his goal, Roderigo says, "It is silliness to live, when to live is torment" (I.iii.308). He apologizes for being so silly but says he does not have the "virtue" to change, to which Iago responds, "Virtue? a fig! 'tis in ourselves we are thus or thus" (I.iii.320). Iago maintains that men make of themselves what they desire to be; men do not follow a course predetermined by any inner qualities. Iago's advice seems to renew Roderigo's resolve even as his threatened suicide gives evidence to the intensity of his longing for Desdemona.