In Act 4 Scene 2, How is Iago able to manipulate Roderigo’s anger to his own benefit?

Roderigo is angry because Desdemona is not his yet. If anything she is out of his reach. Iago still manipulates Rderigo by asking him to follow his plan. If it doesn't work he says Roderigo can take his life,

mean purpose, courage, and valor,

this night show it; if thou the next night following enjoy

not Desdemona, take me from this world with treachery

Iago is dangles the thought of sleeping with Desdemona in Roderigo's face so Roderigo follows him.