I heard on the radio that they did a study on this and apparently if you go one way you are a pessimist and if you go the other way you are a optimist.
I can't remember which way is which though. I will try and look it up.
Edit: I found this but, I am still looking : In the Toilet Paper Personality Test, 2000 people were surveyed on which way they roll their toilet paper, and on how assertive they are in their relationships on a scale of 1 to 10. The results revealed that those “who roll over are more dominant than those who roll under,” meaning they have a Type-A personality. Under-rollers are the opposite, being a member of the more submissive and laid-back niche. Sorry under-rollers, but you’re probably not going to rule to world any time soon.
The study also found that some over-the-roll-people feel so strongly about the orientation of their toilet paper, that they actually admitted to flipping the roll over if they come across a stray under-roll at someone’s house. Now that’s dedication.