Just dropping in again to say a big thank you to all those who helped me out on some of the basics by answering my questions. While I won't be able to actually start playing for a couple of days (not mentioning the fact I probably have a lot of guides to read and tutorials to watch, and that's before even playing against bots), I've certainly got a better grip on the terms, roles and generally what I should be doing and looking out for.
From the descriptions, It sounds like I'll probably like either tank or support roles the most. Jungling sounds overly complex for someone new to the game, and carry sounds too razor's edge for me. Generally speaking, I don't want to be a pain in the ass or a glory hog, which sounds like what carries are good for.
Luckily, despite how venomous a reputation this community seems to have, I'm good at cutting away pointless bitching and finding then taking into account any constructive criticism, so hopefully that's one aspect of the game I won't have trouble with.
Thanks again for all the help.