Download Nexus Root Toolkit 1.9.8 from here, here or here. You can downlod previous version of Nexus Root Toolkit 1.9.7 from here.

Unlocking, rooting, relocking and unrooting simplified! (and much more!)

VERSION 1.9.8 - This program will automatically bring together all the files you need to unlock and root your device in a few clicks, or flash it back to stock and re-lock it. You can also use this program to backup/restore all your important data, flash zips, set file permissions, push and pull files, install apps, generate logcats/bugreports, and much more! With the included file association options, you can perform tasks like flashing zips, installing apps, restoring android backup files, and flashing/booting img files with just a double click! The program includes a full featured interface for automating tasks in TWRP, enhanced restore features, an in-built auto-updater/notification system, ‘any build’ mode, advanced restore features,’NRT- Live Log’ for viewing the adb/fastboot cmds that are run in the background, quick tools utilities, and tools for taking screenshots/screen-recordings. All the latest Android builds and Nexus devices are officially supported including the new Nexus 5, with full KitKat support for all the newly upgraded devices. The program intelligently and selectively downloads the files it needs for your device and makes sure you are using the latest files available. The program can even auto-detect your device and build. This release brings Lollipop support, bug fixes and general code enhancements and optimizations.

Supported Nexus devices:
· Galaxy Nexus: GSM Models (both yakju and non-yakju builds)
· Galaxy Nexus: CDMA/LTE Verizon Models
· Galaxy Nexus: CDMA/LTE Sprint Models
· Nexus S: Worldwide, i9020t and i9023 Models
· Nexus S: 850MHz, i9020a Models
· Nexus S: Korea, m200 Models
· Nexus S 4G: d720 Models
· Nexus 7: Asus Tablet
· Nexus 7 3G: Asus Tablet
· Nexus 7 v2 (2013): Asus Tablet
· Nexus 7 v2 (2013) LTE: Asus Tablet
· Nexus 10: Samsung Tablet
· Nexus 4: LG Phone
· Nexus 5: LG Phone

Instructions:

1. Select the correct device and build (what you are currently running)

2. Configure your drivers if you haven’t already using the driver guide (If you aren’t sure use Step 3 of the driver guide to test your drivers).

3. If you need to, backup your important data.

4. Unlock your device

5. Root your device

6. Enjoy! ^_^

Learn more about each option by mousing over the control, dynamic tooltips will provide you more information, also each button displays a message about what it does first.
So the best way to get familiar with the toolkit is simply to press the buttons and read what it says.

What’s new in Nexus Root Toolkit 1.9.8: November 18th, 2014
· Dynamic web-backed legacy file scrubbing system built. Now in the event of a bad upload, WugFresh can easily upload a new file with the identical file name and upon Masterlist update NRT will automatically handle scrubbing the legacy file.
· Copying CWM Nandroid to computer now works properly on Lollipop.
· ADB Not Found message for performing ADB Sideload operations now details how to properly configure the driver in that state.
· Additional information on hashcheck mismatch msgbox, which now notifies the user updating the Masterlists is the first thing they should try.
· New ‘Post-Flash Factory Reset’ option under ‘Flash Stock Options’, which when enabled will automatically boot the user into stock recovery after a flash stock procedure and instruct how to wipe data & cache, or just cache (if no wipe mode is enabled). This option is designed to help mitigate some issues select users have with bootloops/storage-display-issues post-flash. This option is only available when ‘Force Flashing’.
· New additions to ‘flashstock.bat’ to accommodate the new vendor.img file present on N9.
· QuickBoot app now replaced by QuickReboot (by PhongIT) to accommodate Lollipop support.
· Busybox Installer by Stericson updated to the latest version available.
· Nexus 9 and Nexus Player added (without root support – still waiting on TWRP).

via www.wugfresh.com