They're having fans vote between two versions of the chicken with a chance to win coupons for free chicken. There's an original version and a spicy Sichuan (or Szechuan) version, and original is winning the vote 2-to-1 so far.
I guess if McDonald's in Taiwan can offer fried chicken, roast chicken isn't much of a stretch for Burger King.
The price appears to be $149 NT each or about $5.13 US.