Firstly, go and check out the following video walkthrough for the tweak, after it we will get in details about how does the tweak work:
Once you install BarrelRoll, you’ll need to head to Activator’s preferences in the stock Setting app. From there, you can assign the BarrelRoll action to your gesture of choice. As I always tend to do, I assigned the tweak to a double tap on the status bar gesture.
Anytime you want to make iOS perform a barrel roll, simply invoke the tweak using your assigned Activator gesture and iOS will barrel roll on command. It works at the Home screen, within apps, and you can even interact with iOS mid-barrel roll.
Give it a try on your device, the tweak is available for free at Cydia store via Ryan Petrich’s repo: http://rpetri.ch/repo.