? In a comparison between having a roommate and living alone, i think living alone is more responsibility. There's nobody to call you on your BS when you live alone, just yourself.

E.g. Forget to pay your share of the rent when you live with a roommate? Room-mate yells at you. When you live alone you get an eviction notice.

Self-discipline is about the self after all. If you need another person there to be disciplined, then you are clearly not self-disciplined.

(That said, nothing wrong with roommates, it often makes financial sense and some people like having them, i just dont see the connection to responsibility)