Katy Perry's 'Roar' Expected to Out

RollingStone.comKaty Perry's 'Roar' Expected to Out-Sell Lady Gaga's 'Applause'RollingStone.comIt looks like John Mayer was right when he said that Katy Perry's"Roar" would be a huge hit. According to Billboard, Perry's new single is set to sell 450,000 downloads by the end of the week, eclipsing the new single from fellow pop star Lady Gaga ...