How is Roderigo betrayed?

The Tragedy of Othello is a play full of betrayals, and Iago's treatment of Roderigo is just one example of Iago's capacity for treacherous behavior.
Roderigo is not characterized as a very intelligent man. As well, he loves Desdemona, but she loves Othello. Iago uses this knowledge, taking advantage of Roderigo's indiscretion to manipulate Roderigo. Iago promises Roderigo that Desdemona will be his, as long as Roderigo helps Iago to take down Othello.
Roderigo completely misses the fact that Iago is not trustworthy while Iago takes his money and engineers fights between Roderigo and Cassio to make Cassio look bad to Othello. The knife attack on Cassio ends up being the end of Roderigo when Iago takes the opportunity to stab Roderigo in the back after Roderigo has been injured, killing him.
This merciless act is all the more villainous when the audience realizes that Iago disposes of Roderigo only after he is hurt, as Roderigo is no longer able to help Iago if he is injured. Even more painful is the fact that Roderigo experiences a flash of understanding the moment before he dies, and he takes his last breath knowing he has been manipulated and used.