Unlocking the bootloader and rooting are mutually exclusive. A device can be rooted without being able to unlock the bootloader.
In fact, I've found myself in the odd position once on my Tab 10.1 of replacing the bootloader and not having root access. It was easy to fix but I found that an odd spot to be in.
From Southern California
Tablet: Galaxy Note 10.1 (2014), Phone: Galaxy Note 3
Alma Mater: UCLA (Birthplace of the Internet)