What does the audience learn about the relationship between roderigo and iago?

Here're some differences and relationships between both:

In Othello, Shakespeare begins the play with two foils, Iago and Roderigo at night: one hidden and the other in plain sight.  The former is a villain, the latter a fool, but both are be dark lords of misrule.

Here's what they have in common:

·       Both are targeting Desdemona (Roderigo as thwarted love; Iago as revenge bait against Othello)

·       Both are jealous of Othello

·       Both are expose Desdemona's secret elopement to Brabantio (Roderigo publicly; Iago privately)

·       Both lose their battle against Othello in Act I (the Duke condones the marriage)

·       Both seek revenge in Cyprus (away from the Duke's protection)

·       Both are id-based characters (exhibit child-like behavior and seek immediate pleasure: Roderigo=lust; Iago=suffering of others)

Here's how they are different:

·       Roderigo is public in Venice and private in Cyprus; Iago is private in Venice and public and private in Cyprus: (as such, they are two halves of the hidden, dark side).

·       Roderigo is pure passion (he threatens suicide); Iago is calculated passion (he wants only to wound others)

·       Roderigo pays Iago.  Roderigo is the "money" and Iago is the "purse."

·       Roderigo is a fool.  Iago admits, "I am not what I am" to Roderigo, and yet Roderigo continues to believe and pay him

·       Roderigo thinks his using Iago for his dirty work, but Iago is really using Roderigo to be his scapegoat.  Iago uses Rogerigo to expose Cassio.

Hope this helps!