Consider for a moment how your phone is currently being answered. Professional courtesy is quite often not the standard for many college students. An abrupt "Yeah!" could be listed among the more courteous greetings. The more outrageous remarks will often buy you a major black mark in the professionalism category—even if it was just your roommate acting crazy. A simple "This is ____" is always a pleasant change for a college student call. Make the change today, before the next (or first) employer phone call. If you have a landline, you should also encourage your roommate to do the same.
One final note on phone etiquette: if you (or any of your roommates) persist in the use of creative phone answering lines (trust me, I've heard them all), just remember that the click you hear on the other end of the line may be the sound of your dream job being passed on to Contestant #2.