It is a difficult situation.
In my third year I was living with two people I'd lived with the year before and one new one, in a different (much nicer/bigger) house. Me and my friend had done the looking and ringing landlords on the day the lists came out, as the year before we'd left it late and ended up with a **** house.
Me and my friend had small rooms in the second year, the one person we'd lived with insisted she wasn't having a small room because she hadn't got the room she wanted the year before, even though she'd still got a big one (and it was her who stopped us getting the house the rest of us had wanted, which she conveniently forgot).
We picked straws in the end but then ended up swapping around anyway because one person wanted the medium room rather than one of the big ones. My friend ended up with a small room for both years, but then she went home for at least three days every single week and hardly had any stuff really, although it was quite unfair that the other girl had big rooms both years when we all paid equal rent.
To be honest, with the way your friends are acting, I'd be tempted to tell them where to go, as they have done nothing to help and it doesn't sound like they are there much anyway. Maybe suggest swapping rooms after half the year, then hopefully when it gets to then they won't be bothered about actually doing it.
Or say that if you live together next year they can have the bigger rooms, or they can use the living room more/be in charge of the remote or something.
Or, just pick straws and hope you get the room you want.