Katy Perry's new song "Roar" is off to a roaring sales start, with industry forecasters suggesting it will move around 450,000 downloads by the end of the tracking week on Sunday (Aug. 18). Meanwhile, fellow diva Lady Gaga is also off to a handsome launch with her new single "Applause." It's heading for a bow of perhaps 200,000 to 225,000 downloads.
