Good question...
Based on the Food Lovers Companion...
Roast
v. *To oven-cook food in an uncovered pan, a method that usually produces a well-browned exterior and ideally a moist interior. Roasting requires reasonably tender pieces of meat or poultry. Tougher pieces of meat need moist cooking methods such as braising.
Bake
To cook food in an oven, thereby surrounding it with dry heat. It's imperative to know the accurate temperature of an oven. Because most of them bake either hotter or cooler than their gauges read, an oven thermometer is vital for accurate temperature readings.
By the way,
Cook's Illustrated recently had an article on oven thermometers. They even tested their own ovens for accuracy and were amazed at the variations within each oven and how different they were. Within each oven there were ranges of at least 50 degrees
inside the oven. It was a very interesting article. One of the many factors which affected oven temperature within the oven is where the heating element resides and how long it takes to cycle to try to maintain the temperature you have on the dial (if that's accurate in the first place). The element comes on at intervals as specified by the manufacturer. Check out the article if you get a chance, it's very enlightening.
Also, for any Christopher Kimball (Editor of
Cook's Illustrated) here is where you can find his weekly column
The Kitchen Detective