I have a roommate who is constantly my other roommate, for example, when he doesn t flush the toilet

First of all, according to what you said, this should not be required of you, the toilet should have been flushed, and if you watch a movie, you should consider others when there are people in a common place, obviously these are all small things in life, not enough to describe with heart. In addition, it shows that he has good habits, or that he has developed a habit of living in the same dormitory with others before, and when a habit becomes natural, then he will take some things for granted. You can try to change your habits, and you can also communicate with him and tell him that there are some habits that need to be formed slowly, and I hope he understands.

If he uses a magnifying glass to see everything and wants to be perfect in everything, then he may be a little obsessive-compulsive or similar, and psychological counseling is recommended. But after all, live in one place and don't exacerbate the contradictions. It's about finding a way to resolve it.

This person is selfish, arrogant, self-centered, and stay away from him.

First treat him with a normal heart, if you go too far, you have to resist, and occasionally remind another roommate to pay attention, as for other things that are not your business, don't care.

You also look for opportunities to ask for accusations against him. Let him feel your feelings.

It's a flashlight, and you can't see yourself just by looking at others! The difficulty, it's all the same up to that point.