Charcoal-roasted teas have a very distinctive character that is usually quickly recognizable. When the tea is both carefully roasted and brewed optimally, the roasting adds a rich carmelized sweet note that heightens the flavor of the tea and rounds out or balances other notes in the tea. When charcoal roasting (or brewing) is done carelessly, what is left is the flavor of the charcoal which overwhelms the taste of what otherwise might have been a marvelous tea.
Teas that lend themselves to charcoal roasting include Taiwanese Dong Dings, Wuyi varietals grown in China or Taiwan, and Ti Kuan Yin varietals grown in China or Taiwan. These teas are typically brewed in hotter water (190-200ºF), but I notice that if I brew them in slightly cooler water (175-185ºF), the sweeter notes become more dominant, the tea has a smoother mouthfeel, and the charcoal roasting is not as pronounced.
Bon Teavant carries a traditionally harvested and crafted Charcoal Roasted Dong Ding which sometimes has a little more charcoal flavor than I like, so I brew it just a hair cooler and longer, which diminishes the charcoal flavor and still creates a rich, smooth, roasty cup of tea with a terrifically smooth mouth feel. If you are a person who likes to taste the charcoal, that is there for you also. Either way, this special tea provides an extremely satisfying cup that is distinctive and memorable.