If this is locally on the same machine try:
mysql -uroot -p<password>
Notice no spaces.
Also did you actually setup a default root password after installing mysql? If you su to root, you can actually connect by just typing:
You can update the passwords once in mysql that way, etc.
mysql> GRANT ALL PRIVILEGES ON *.* TO root@localhost IDENTIFIED BY 'new-password' WITH GRANT OPTION;
And to commit the changes do a:
mysql> FLUSH PRIVILEGES;
I'd suggest creating another user though, not necessarily but I tend to not use root as a user on anything.. just a habit..