When your business is closed for vacation or holidays, it’s imperative that you set appropriate expectations for a callback and to provide an alternative coverage option, if available. The following greeting accomplishes this succinctly.
“Good afternoon. You have reached the office of [your name]. I will be out of the office beginning on [date] and will be returning on [date]. Please leave a brief message with your contact information, and I’ll be sure to get back to you as soon as I return on [date]. If this is an emergency or you need to speak with someone before I return, please contact [name of colleague/supervisor], [their job title], at [their phone number].”

I have amnesia and can’t come to the phone at the moment. I feel stupid talking to everyone that I don’t know. So why don’t you forget about leaving your original message, and instead tell me my name and something important about myself. Thanks a lot.
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 your roommate answering your phone and 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.