The root password will only be used to login to the system from the console. Enter in a password that is at least six characters. Mixing numbers, letters and avoiding whole words is recommended. A few examples would be to take a word like lockbox and break it up with some letters and numbers. You can use the following characters as well:
| ! | @ | # | $ | % | & | * | ( | ) |
So you can end up with something along the lines of:
Which will be almost impossible to guess even more difficult to crack.
You have to enter the password a second time to verify they match.