dss,
I think that it’s a good sign that you thinking ahead and trying to anticipate the situation. At least you are trying to come up with a plan to handle the future. I agree with others that hooking up with a roommate can be a bad idea, it is very difficult to avoid someone when you live in the same house.
However, you might be getting ahead of the situation, you don’t even know these women. You have no idea about their personalities and they don’t know much about you. Yes, according to you they are both attractive, but if you are really looking for a LTR that should probably not be what you based your relationship on. Even sex with a very hot and sexy girl can get old after a while. Get to know them, maybe one of them will be great relationship material and the other one may annoy you, or they may both annoy you. Life is full of tough choices, be ready to make them, don’t shy away from them.
“knowing is half the battle”