I'm going to tell my roommates that if we have a party I want one person specifically excluded.
Why do you want one person excluded from the party?
It's no one that you know. Just know that they're lame and I don't want to deal with them.
Maybe you can work out your differences with this person, or at least try to be cordial with them. If they're a friend of your roommates' they may want them at the party.
I don't need your advice. It's not your place to tell me what to do.
You should talk to your roommates and tell them how you feel. You can all discuss the guest list together and come to an agreement that you can all be happy with.