After defeating the Bills, the Steelers stayed home to take on the visiting Lions.  They started off scoring in the 1st quarter as Ben Roethlisberger found Antonio Brown on 2 consecutive TD passes from 34 and 47 yards out for leads of 7-0 and then 14-0.  The Lions were able to get on the board as David Akers nailed a 35-yard field goal to make the score 14-3.  The Steelers managed to pull away by 2 touchdowns as Shaun Suisham nailed a 25-yard field goal for a 17-3 lead.  The Lions drew closer as Matthew Stafford found Calvin Johnson on a 79-yard TD pass shortening the lead to 17-10 not long before Suisham nailed a 34-yard field goal to make the score 20-10.  Just then, the Lions managed to take the lead scoring 17 straight points when Stafford found Calvin Johnson again on a 19-yard pass making the score 20-17 and with the Lions taking the lead as Joique Bell ran for a 4-yard TD moving them ahead 24-20 and then finally wrapped things up in the first half as Akers nailed a 19-yard field goal to take a 27-20 lead at halftime.After the break, the Steelers got back to work as Suisham nailed a 21-yard field goal to shorten the Lions' lead to 27-23.  They took the lead in the 4th quarter as Roethlisberger found Will Johnson on a 1-yard pass making the score 30-27.  After a failed fake field goal attempt by the Lions, the Steelers set the ball up at their own 3-yard line.  Due to a huge penalty against the team, the Steelers were able to move further down the field and seal the win for themselves as Roethlisberger found Jerricho Cotchery on a 20-yard pass for a final score of 37-27.
Question: How many touchdowns did Roethlisberger throw?
Answer: 4