Rolls For All Seasons

So it has come to my attention today there is a great dilemma facing most people, a question I fear no one may have the answer to. What is the difference between a Spring roll, summer roll, autumn roll, and winter roll?

I was about to order some cuisine of the Chinese persuasion, when the issue hit me right over the head. I saw all four rolls listed on a menu. I had been browsing a site called seamless web, the lazy persons way to food consumption, to which I have become addicted to, deciding which of the thousands of Chinese restaurants in Manhattan to choose. Of course there were no rollover descriptions on them, urgh the torture. I quickly polled my coworkers, but no one had any idea. Are they classified by their outer shells, is it the meats or lack there of inside that give them their names, or is it some historical story of seasonal consumptions past, that identify these little mysteries? This shall need further investigation.