BATON ROUGE — A Baton Rouge judge signed a preliminary injunction on Friday that paves the way for LSU to roster fifth-year player RJ Luis, according to court documents. Luis, a former Boston Celtics guard, was among fifth-year players LSU attempted to roster in Will Wade's first season; other than Luis, 14 of the 15 players LSU signed have played for the team so far.On Oct. 28, a judge placed a temporary restraining order on the SEC to allow Lu…