Like others are saying, rootless is there for a reason and should not be disabled. That said if you know what you are doing then you can use the following process:
- Restart the computer, while booting hold down Command-R to boot into recovery mode.
- Once booted, navigate to the "Utilities > Terminal" in the top menu bar.
- Enter csrutil disable in the terminal window and hit the return key.
- Restart the machine and System Integrity Protection will now be disabled.
