I think to get a true understanding of the different roasts, it would help a lot to visit a high-end coffee shop that serves really good coffee, because those baristas would know how to brew a specific roast. And I mean a place that brews specific cups for the customer, like Philz in San Francisco. You can't brew a light roast like a medium roast, and you can't brew a medium roast like a dark roast. I was a shocked as anybody when I discovered how good a good medium light roast can be because I always considered myself a dark roast guy. I was equally shocked to discover how good a dark roast can be when brewed correctly. But if you try to brew a medium light roast at home like you would a dark roast, you're gonna be disappointed, regardless of how good the coffee is. Right now, I can say I don't have a preference. They're all good! ...Provided they are good coffees to start with.
I think once one realizes how good a medium light roast can be, he can begin trying to teach himself how to brew it perfectly - at home. But it's a long process - a lot of trial and error - but fun at the same time.
When I brew a medium light roast relative to a dark roast, I use more coffee beans, a finer grind, a longer brew time, and I make sure the water is at the high end of the acceptable range, which would at around 205 F, but no higher.
Here is an example of a good coffee shop.
"I guess the difference is tasting something that actually has all the right numbers for the first time. And that's a totally different way to experience the coffee."
-Ben Turiano