To see your old roommate in your dream suggests that there is a lesson that you need to acknowledge from that former relationship and apply it to a current life situation. Perhaps you need to incorporate aspects of your ex-roommate with your own self.
To dream of your current roommate indicates that there are issues that you are not confronting with her or him.
To dream that you are looking for a roommate suggests that you are ready to incorporate a new and unknown component into your life. You are receptive to change.
If you don’t have any roommates, but dream that you do, then it means that you are looking for a friend or for companionship. You want a friend who you can share your feelings with, who you can be open with and who you can talk to about anything.