If you want to Rom or root your device the best phone for you is a phone that is easily bootloader unlockable. Once you have your bootloader unlocked you can install a custom recovery which allows you to flash supersu.zip to root. You can also flash roms and make complete nandroid backups with a custom recovery.
On new Motorola devices like the Moto G and Moto X Pure you get a warning message prior to the bootscreen telling you that your device has an unlocked bootloader and reminding you that Motorola is not responsible for any changes you have made to your device which damage it. There is now a flashable zip which will rid your Moto G 2015 of the pesky warning screen. Grab the zip file from the link below and flash it in TWRP. Pretty simple!
via XDA