A few Fedora versions ago, and if you install the ‘Fedora Workstation’ version, root password is never set.

Warning: This is not the case when installing Fedora Everything.

You get a user with sudo privileges. To set up root password you have to do the following:

[murphy@eva02 ~]$ sudo -i
[sudo] password for murphy: 
[root@eva02 ~]# passwd
Changing password for user root.
New password: 
Retype new password: 
passwd: all authentication tokens updated successfully.
[root@eva02 ~]# 
logout
[murphy@eva02 ~]$ su -c 'echo lolo' # Checking with my password
Password: 
su: Authentication failure
[murphy@eva02 ~]$ su -c 'echo lolo' # Checking with root's password
Password: 
lolo

This how-to was taken from this nice video.