Roderigo is a relatively minor character in William Shakespeare's Othello in terms of the attention paid to him in the play, but he is still a key character who serves as a contrast to other characters--he is honest where Iago is not, he is just as unaware of Iago's perfidy as is Othello, and he is as innocent in his way as other characters about whom Iago lies. Roderigo also serves the important role of pretend lover to Desdemona, a role he fits because of his innocent admiration for her, something Iago can twist into a form that seems anything but innocent. Another reason why Roderigo has to be considered important is that he is the first person in the play to speak, and thus he helps set the tone, outline the plot, and illuminate all that will follow.
In those opening lines, Roderigo's friendship with Iago and his trust of the other man are apparent. He makes reference to how close the two have been in his opening lines:
Tush, never tell me! I take it much unkindly That thou, Iago, who hast had my purse As if the strings were thine, shouldst know of this (I.i.1-3).
This is also where Iago expresses his hatred of Othello and gives a reason--Othello has passed him over for promotion:
. . . Three great ones of the city,
In personal suit to make me his lieutenant, Off capp'd to him; and, by the faith of man, I know my price, I am worth no worse a place. But he, as loving his own pride and purposes, Evades them, with a bumbast circumstance Horribly stuff'd with epithets of war, And, in conclusion, Nonsuits my mediators (I.i.10-18).
In this first scene, Iago and Roderigo seem to be acting in concert, though it is clear that Iago is the dominant force. The two friends awaken Brabantio to inform him that his daughter has run away with the Moor, Othello....