My roommates treat me as a joke and always play with me. How do they change their views on me?

First of all, I think you should review your words and deeds, and don't joke with such people easily at ordinary times. Even people who are far away from such people and don't know how to respect others are not worthy of respect.

Have a good talk with him on an appropriate occasion, tell him what you think and let him know that playing with you all the time will hurt your friendship.