I think a roommate relationship is very different from others, because you are living together and sharing the same space, but there is no obligation to share emotionally or be involved in anything together. Because of this, there is great potential to have a good roommate whom you might never be friends with, as long as both of you have good solid roommate etiquette.
The best way to maintain this is to enter the roommate relationship/agreement with a contract. I've had several roommates and always utilized a contract. This made things so simple! Because if problems ever came up we could always refer to that contract, and if either one of us wanted to do something outside the contract agreement, we would have to discuss it first and make certain the other would be alright with it.
One of my roommates was someone I only roomed with for about six months - I never did like her very much and have never contacted her outside our rooming together, but she had great etiquette, and if it ever came up I wouldn't mind being her roommate again.
Another example is a roommate I developed a great friendship with and with whom I still keep in touch. However, she was a terrible roommate. If we'd stayed roommates any longer than we had, it likely would have ruined our friendship.
Then, I've had a couple more roommates who fall in between the extremes of these examples. One of them was someone who had frequent bouts with depression, who had fairly decent roommate etiquette, and who became a pretty good friend. Her depression wasn't a problem for me, because I just recognized when she needed some time to herself and kept a bit more careful eye on her when she was really struggling, then left the rest of handling her depression to herself.
So - I think the important thing in starting a roommate relationship is not necessarily looking for someone you like, but establishing a contract and looking for somebody who would be willing to live by that contract. It could be a good idea to include something in that contract where your potential roomy could have established code words or something of the like for when they recognize your depression seems to be getting out of hand, and for when you need them to give you some extra space.