I am going to let my roommate know that his friend has to leave or he does.
If he refuses to leave what do you plan on doing?
I will insult him. I am done putting up with him. He thinks of money before his own friends.
Room mates are expected to be respectful of each other's guests. If you deliver an ultimatum then they will become upset. Even if you are trying to look out for them, they'll feel like you're being bossy.
See what I mean?! He's thinking only about money!
You should do your best to be respectful to the guest that your roommate is bringing. Whether you feel you can get along with them or not, just know it is temporary.