The Roommate was one of those movies where you absolutely knew what you were going to get, right? Sure, there are all kinds of thriller sub-genres, but once you start narrowing down, the plot is going to start getting predictable. If you’re in an obsession thriller, such as Fatal Attraction, and you see a small fuzzy animal somewhere around the main character? Prepare to cringe. And if you’re in a lesbian obsession thriller, such as Single White Female, and you see a boyfriend somewhere around the main character? Prepare to cringe about that too, although probably not in the same way. Because, seriously, and with all due respect to Steven Weber, but I feel worse about the bunny.
Not that knowing what you’ll get is a bad thing. Sometimes, it lets you take the time to appreciate the performances all the more when the plot is devoid of surprises. Take our obsessor, Leighton Meester. You might appreciate the dead stare she affects when she is angry, but that’s nothing half as creepy as the bloom of hope in her eyes every time she thinks she’s done something that this time will finally, finally get the obsessee to understand that she’s been right all along and this really is the way things are meant to have been. Of course, sometimes knowing what you’re getting leaves you with the time to ask too many questions, too. It’s always an interesting thought exercise to determine how the police will react to these events. Will there be enough witnesses for her to feel comfortable explaining what happened? Must she run away, her life forever shadowed by the tragedy even though she won? And this type of movie never addresses those questions, so if it leaves you with the time to ask them, and you can’t come up with satisfactory answers? Well, I at least think that’s a bad sign. Probably great numbers of people won’t ever mind, though.
That’s cool, I’m sure I’m wrong sometimes too, so no reason to beat them up about it.
 I hesitate to narrow the field in that way. It’s not that the characters in obsession thrillers necessarily want sexual relationships with the objects of their obsession, and it’s certainly not like that is the prescribed way for the obsession to start. It’s just that once the obsession exists, there is always always a sexual element to it.