The Piston’s 15 man roster is set with Detroit yesterday releasing training camp invitees Terrence Williams and Jonny Flynn, both lottery picks in the 2009 draft. The Pistons, who are 3-and-3 in exhibition play, have their next to last pre-season game tomorrow night at Minnesota and then host the Hawks on Friday.Detroit’s regular season opener is on Halloween a week from tomorrow at the Palace against the Houston Rockets.