My city has a small Jewish population, which means it's highly unlikely I'll find a Jewish roommate who also keeps kosher. I think I've figured out how to make the kosher kitchen work (though I'm always open to suggestions from people who have been in my place before), but what do I do about Passover? Is it enough to ask one's roommate to keep her chametz on her side of the kitchen, contained in a receptacle?
If you must room with a non-observant roommate, the ideal would be to talk to her about the possibility of keeping kosher while in the apartment. You'd be surprised to find how many Jews are actually willing to keep kosher if merely presented with the idea. At the very least the apartment should be kept kosher for the eight days of Passover. It shouldn't be too hard to find a Jewish roommate willing to make this compromise; because most Jews anyway observe Passover in some form or another. (And besides, I wonder: Would you want to room with someone not willing to compromise for one week?)
However, Jewish law does not recommend sharing a kosher kitchen with someone who does not keep kosher. For one, there's the question of the person's knowledge of the kashrut laws. Second, when push comes to shove, how reliable can we assume a person to be if they themselves don't fully subscribe to the idea of keeping kosher? If she's cooked all day for the dinner-party you two are planning for a bunch of friends, and 10 minutes before the guests arrive, she realizes she's cooked all the meat in dairy pans, will she tell you? Or will she think, "Is it really such a big deal if just this once the meat was cooked in dairy pans? I mean, the pans were totally clean, and what Zippy doesn't know won't hurt her."
Such kashrut mistakes are quite common, so you need a kitchen partner whom you know you can rely on 100 per cent of the time to inform you if something's gone wrong.
For further reading, see the book After the Return by Rabbi Mordechai Becher and Rabbi Moshe Newman, Feldheim Publishers.