In 2005, Jamie Dimon was taking over as chief executive officer of JPMorgan Chase when he lured a Goldman Sachs foreign-exchange derivatives trader to join him. Troy Rohrbaugh turned into a lucrative hire. He helped the bank earn hundreds of millions of dollars during the 2008-09 financial crisis, modernized its trading technology and moved JPMorgan from ninth to first in global rankings for foreign exchange over the course of a decade. On Thursday, Dimon and the board handed Rohrbaugh the title of co-president and gave him responsibility for running Chase Bank and the rest of its sprawling consumer business. In…