cheaper than packs. This is true everywhere
as far as I know.
You can decide the size of your cigarette each time. This is especially helpful when you just want a quick smoke between classes, for example.
You can mix and match different flavors of tobacco to fit your mood.
Rolling your own cigarettes makes you good at rolling joints.
When you roll up a cigarette in public, you're almost guaranteed to get a funny look from one or two people who think you're rolling a joint. I've found this is a good way to meet people (even better than asking to use someone's lighter). The downside is that if you happen to have illegal substances in/on you, this attention could get you in trouble.
People are often impressed at your ability to roll a cigarette; especially if you can do it w/ one hand while talking on the phone :)
Rolled cigarettes are stronger, so you don't need to smoke as often to satisfy your nicotine quota (that's not to say that you won't smoke as often though).
Rolling is fun!
I think these outweigh the disadvantages, though I do sometimes get lazy and buy a pack of Camel Filters.