I'm going to let people in my house without my  (ex)boyfriend/roommate's permission.
What do you think he would say if you did that?
I don't think he would like it if someone was over without him knowing. It's none of his business.
You should do whatever you want now, that person is your ex. He has no bearing over you nor should be able to control who you invite over. If he can't respect that then he shouldn't be your roommate either.
True. He's acting so controlling. I don't care anymore.
Just because he's an ex it doesn't mean he's entitled to certain things. You need to set boundaries between you two in order to avoid him being too controlling. Otherwise you might just be better off finding a different place to live.