ah, roommates, having lived in several student homes I can write a book about it. There were two categories, the ones who you could reason with and the ones that were plain a-holes that only took care of their own needs without any regard to others. To deal with that last category of people you needed either aggression or retaliation. Did you know that 1 in 20 people is a true asshole?? I guess they have their place in evolution, we have to deal with them however.
There is a difference between outing your emotions against the ones who are really responsible for them and outing them against the people who just happen to be at the wrong place at the wrong time or are simply easy subjects to project anger on.
The thing to find out is which of the two is applicable to you. When you are annoyed by someone, try to out that emotion right away. It will be less intense and it is healthier. You can always apologize later if you feel you went a bit too far.
Thanks for bringing this up, I sensed tension when I thought about certain people from the past.
Dumping your wet laundry on the dirty floor because an a-hole felt like doing his, sometimes even when the cycle wasn't even finished. - I forgive and let go easily.
Not doing the washing up so the next day there was nothing available to cook with. - I forgive and let go easily
Turning the stereo to 11 and then leaving the house - I forgive and let go easily
Noticing your pizza, the only thing left in the house to eat for you that night, had been eaten by your lazy roommate who didn't feel like going to the shop - I forgive and let go easily.
Co-students during a project that were doing the least possible amount of work and getting the highest grade. - I forgive and let go easily.
C0-students not showing up during a project whenever they felt like it and not even apologizing for it. - I forgive and let go easily.
Noticing stuff you were missing and that you asked several times for was lying around in their room - I forgive and let go easily.
Coming back home after two weeks of summer holiday, in a house that reeks of garbage because your roommate, who never did anything anyway, felt it wasn't his responsibility to bring out the trash. - I forgive and let go easily.
I can go on and on...

One of those assholes is still a friend, great guy, you just don't want to live with him in one house. Others I have never seen again, not to my regret.