Think its a good idea if I tell my classmates and instructor how shitty of a person my roommate was on a trip?
Why do you want to tell people bad things about your roommate?
Because he's a bully, and I'm tired of his narcissistic, insensitive behavior.
If you have legitimate complaints about your roommate, you would be wise to go to your instructor and calmly lay out the problem. But if you go tell all your classmates, you are involving people who don't need to be told and you might be perceived as a bully yourself.
I'm clever, and my goal is to make my roommate look bad in front of everybody.
Its still wrong to tell everyone this when it should be handled by the people in authority. You should let them handle it and leave everyone else out of it.