A two-alarm blaze on a South End roof deck caused about $200,000 in damage Tuesday night, the Boston Fire Department said. Firefighters responded at 8:50 to the seven-story yellow brick condominium building at 492 Massachusetts Ave., department spokesman Steve MacDonald said. The building was evacuated, MacDonald said, and there were no reported injuries. He said the fire appeared to be caused by a charcoal grill, which was being used on the deck in violation of a city ordinance. MacDonald said the blaze caused extensive damage to the roof, and that residents were able to return home after it was extinguished.