The Vancouver Indy Coffee Scene

Coffee with its original caffeine content removed. The decafeination (decaf) process involves immersing the un-roasted coffee beans in a solvent to remove the caffeine. The conventional process involves reusing the decaffeinating solvent again and again, thereby saturating the solvent with coffee flavours and preventing further transfer of flavour from the beans to the solvent. Commonly used solvents include water (see Swiss Water Process), benzene, ethyl acetate, methylene chloride (MC), and carbon dioxide (CO2).

The Swiss Water Process is by far the better process or decafeination, which results in a far better product then any other process delivers.

Dark roast means that the coffee bean has been roasted to a higher temperature and typically for a longer period of time. This causes all of the flavour molecules stored within the oils of the coffee beans to be roasted away. Darker roasts tend to have a larger body and a strong taste, many of the acidic and varietal qualities have been roasted away. This leaves the roast with less depth in the roast but wider body and ashy flavour.

Author’s note:
You can hide the imperfections of a bean in a darker roast as a lot of the original flavour has been replaced in the roasting process.

I have no idea what high roast, continental, or Vienna roast is. It may be used by some chain cafes for marketing terms but as a commonly referenced term in Vancouver it is rarely used and not part of the normal lexicon of independent cafes in my opinion.