Wow, big day for root things on the Nexus 4 and 10, eh? First off, official ClockworkMod Recovery is now available for the pair, either directly from the CWM site or through ROM Manager, which was also updated today to support Android 4.2. While the latter can handle flashing the updated recovery, Koush himself advised users to flash via fastboot to avoid any potential issues with the process.
Koush also took it upon himself to update the Superuser application for 4.2, just until the original developer can get around to updating the official application in the Play Store. Alternatively, you can also flash SuperSU, which was developed by Chainfire.