i'm sure you could find green beans somewhere in calgary. yes, some beans do better for darker roasts than others. i did a bit of internet searches for the "how to" and the type of beans. i'm getting 15lbs of beans from http://www.levelground.com/
they sell fair trade beans, you have to email and ask for green beans.
currently i am roasting with a popcorn popper with success!!
the lighter a bean, the higher the content of caffeine. the first few batches that i roasted were a medium blend ( a light coloured bean) and after a few cups my wife was complaining of too much caffeine, as we are used to very dark roasts!!