title_body: Roasting my coffee beans
upvoted_answer: Your first question isn't clear exactly.  All drinkable coffee has been roasted first, as raw coffee beans are not edible. I've read that re-roasting beans isn't practical for some reason that I'm not clear on, but I agree with Peter Pei Guo's, comment about why you would want to re-roast coffee in the first place.  
  
  Immediately after roasting, coffee beans produce carbon dioxide gas as a result of the chemical changes happening inside the bean.  This gas takes some time to be released from the interior of the bean, anywhere from 3-5 days.  
  
  I've brewed my own home roasted coffee immediately after roasting to see if this is really true, and yes, it is.  
  
  Immediately after roasting the coffee has a really harsh, sour taste from the acidity that accompanies carbon dioxide gas (carbolic acid).  It also foamed (bloomed) really violently with the addition of hot water.  After resting the roasted coffee for about 5 days, the coffee from the same batch of beans tasted great. 
  
  One of the indicators of freshly roasted coffee beans is the bloom that they produce as some residual carbon dioxide gas is released with the addition of hot water.  
  
  As time passes and the beans begin to stale a bit, the bloom lessens, then disappears.  After properly resting freshly roasted coffee however, the small amount of residual carbon dioxide doesn't affect the taste.  Immediately after roasting however, the carbon dioxide levels are too high to allow good tasting coffee when brewed.