The Australian international winger has put pen to paper on a new deal which will tie him to the club until the summer of 2012.
Emerton Pens New Deal
"This is great news for the club," Rovers chairman John Williams told the official Rovers website.
"Brett has been an excellent servant over the last five years and we are delighted to have agreed a deal which keeps him here for another four years.
"He's a very willing member of the squad and a real club man."