You can simply reset the root password by running the server with --skip-grant-tables and logging in without a password by running the following as root or with sudo:
service mysql stop
mysqld_safe --skip-grant-tables &
mysql -u root
mysql> use mysql;
mysql> update user set authentication_string=PASSWORD("YOUR-NEW-ROOT-PASSWORD") where User='root';
mysql> flush privileges;
mysql> quit
# service mysql stop
# service mysql start
$ mysql -u root -p