By Zach Koons Pittsburgh Steelers quarterback Ben Roethlisberger officially announced his retirement from the NFL on Thursday in a touching video posted to social media. After 18 seasons in professional football, all of which he played in Pittsburgh, Roethlisberger has decided to hang up his cleats for good. He’ll leave behind a legacy with Steelers that includes two Super Bowls and one of the most accomplished passing careers in NFL history. Thursday was not only an emotional day for Roethlisberger and his family, but also for the rest of the league. Past and present players, media members an…