check on web MD.com

Try not to have sex with your roommate.

I'm being a little flip, but...
the herpes virus is enveloped (has the same layer of fats and proteins as a human cell membrane).
Enveloped viruses tend to be pretty wimpy when exposed to the elements - they're very prone to dehydration, etc.

I would hope you weren't sharing razors with you roommate anyway.

Quarantine her in her room. You can slip rations under the door.

Like seraph suggested, the virus won't survive outside of the body for long. I know oral herpes can be passed through mouth to mouth contact, so if she has that type I wouldn't share drinks.

If it's oral herpes it can absolutely be passed handling used silverware or cups etc. It's highly contagious from the onset of symptoms, which is usually a tingling on the lip, until they become full blown sores, break open and scab over. Usually outbreaks last from 5-7 days. As we all know from the Valtrex commercial, it is still possible to spread herpes even when you are not having an outbreak. Just use common sense and make sure your roomie does too.

ixnay on the medical advice from chat boards
Here's an article from emedicine. It describes some spread via respiratory droplets, but I've never seen anyone on respiratory precautions for cold sores. I'm pretty sure you need physical contact for spread. But really, don't share razors. eww. hep c can definitely be spread that way. regardless. eww.

Here's the article. If you're really worried, talk to your doctor.
http://emedicine.medscape.com/article/783113-overview

Don't have any kind of sexual contact with him/her.

Ummm don't have unprotected sex with them. That is about it. Also, obviously you don't want to share toothbrushs or razors as a precaution. No, you cannot get it from toilet seats, towels, or sheets, it is only spread from skin to skin contact with the site of infection. Other than that, stop being so paranoid and perhaps offer your friend some compassion, I doubt that she is having an easy time right now. Also, do not tell anyone about this, I am sure it is embarassing enough for her already and she obviously has trust in you to even tell you. Please realize that 25% of the population has genital herpes, and many people do not even know they have it and could be spreading it around. My friend has it and she has been with her bf with 4 years, they have had sex without condoms several times and he has never had any symptoms of it. I am just saying that I think you are being really paranoid!

"We are what we think. All that we are arises with our thoughts. With our thoughts we make the world." Buddha