Trying to Understand Roast Styles...

When roasting coffee, the moment you stop your roast defines what kind of flavors you'll experience from those beans. In actuality it's a little more complicated than that but for the most part what defines the characteristics of a given coffee is by what temperature or how far into the roasting process you choose to take the beans. You'll notice, when roasting at home that coffee progresses through stages during roasting, The first part is rather uneventful, moisture exits as the beans warm up, further in, the beans are changing colors from greenish gray to yellow and spotty maybe beige, then as they approach the early tan and brown stages ( looking a little more like roasted coffee) strange events occur, popping starts, the beans sound like pencils breaking, it swells and the popping gets crazy. After you hear the "first crack" coffee is actually drinkable, it may not be very desirable but its drinkable. Every moment and every degree that the roast progress's presents the roast with different qualities. After roasting for a while you get to know certain coffee's and when they taste the best and you get to know our own tastes and how you like your coffee to taste. With that knowledge you stop the roast at that very second and you have your perfect cup of coffee. That's the beauty of home roasting, your in control.
So now, a little about what all this means. The nomenclature for roast degree's exist a few different ways, there is some older and regional ways of naming roasts, there are some more traditional ways and there are also the roasting communities very scientific color naming system that relies on a machine that measures the color density of beans and assigns it a number, its extremely accurate and consistent, ensuring that a light brown roast from Brooklyn is the same as a light brown roast from Poughkeepsie.
Anyways here is a pretty standard description that you'll find out there:

Cinnamon this is right after first crack begins, if your reading a thermometer the bean mass would read around 400 degree's. The taste is probably grassy, bread-like. The bean surface is dry and light brown maybe spotted depending on the origin.

City Roast is next, this roast starts around 410 degrees to 415. Here is where the origin flavor of the coffee is at its peak. The acidity is usually high, the body is developed and the aroma is peaking. The bean surface is almost completely uniform in its light brown-ness and the surface is dry. If your tasting for origin, this is where you'd stop.

Full City is a very nice place to stop because at 425-430, even 435 degree's, the coffee still retains a good bit of its origin distinction but starts to take on some of the sweetness from caramelizing sugars. Aroma and body are well developed. The beans are dark brown, smooth with perhaps a spot or two of oil.

Vienna and Espresso roasts are next, around 445 to 455 degree. Espresso really depends on region but if you want an espresso roast anywhere in this window would be good, origin flavor is diminishing and being replaced by heavy sugar caramelization. This is where roast flavor is starting to take center stage. The surface is shinny more oil and dark brown in color.

French roast is around 460-470 degree's F. We are talking pungent dark dark bean color, oily surface, all origin flavor is gone, sugars are developed and the coffee tastes bitter sweet. the body thins at this point in the roast and the aroma is very distinctive.

Dark French/Spanish 470 degree's and above, if your at this point, you probably can't see the beans in your kitchen from all the smoke and it doesn't matter cause you'll be reaching for the fire extinguisher. Fire is close. Even if you did choose to roast to this degree, the coffee would taste burnt and industrial, thin body, oily. It can be done right and many people will drink their coffee in this style however as a home roaster, it could be dangerous.