No need to root your Nexus! Use your external USB flash storage devices on your Nexus by installing OTG Disk Explorer. You can also use this application as a nice file browser.
The fully featured Nexus OTG Disk Explorer is easy to use with its user-friendly interface and intuitively designed icons. And the best part - NO ROOT NEEDED and it is absolutely FREE.
Some of the main features of the application:
• Works on all Android devices.
• Doesn't need to root your Nexus.
• Process manager gives you the chance to kill running processes and monitor the available RAM memory.
• Quick access icons for you SD card, Camera folder, Bluetooth folder, Downloads and Music folder.
• Recognizes all common file formats.
• Cut/Copy/Paste options.
• Rename or create files/folders.
• Organize your folders - Search, Sort and Create new.
• Change the visualization of files and folders - list or grid.
• Select multiple files. Automatically shows the size of the selected files.
• Properties that give you a detailed information about every file or folder - Type, Path, Number of files, Size, Last modified, Total available space and Available space.
• Share files.
• Delete.

The only requirement: your USB flash drives must be with FAT32 file system in order to be recognized.
OTG Disk Explorer is your easy USB mass storage enabler for all your devices.