Default How do I keep my TA keys with my Z2 if I unlock the bootloader?

I was just looking at how to root the Z2, and I noticed that to root it, you first have to unlock the bootloader and install a custom recovery, but unlocking the bootloader removes TA keys, so you first have to back them up, but backing them up requires root access. Am I missing something here or is it impossible to keep your TA keys to root?
Current devices:

Xperia Z2 (PAC-Rom nightlies)
Xperia Z2 Tablet (PAC-Rom nightlies)
Xperia Play 4G (CM11 nightlies)