Rooting will ONLY damage your phone if you don't properly take the time to educate yourself with the associated rooting terminology, apps and methods used to unlock/root your device.
Before you ask, will rooting void your warranty? Yes but only while its in the rooted state. That is why there is always a return to stock method in the event you just don't want to be rooted anymore or you need to have your device serviced/warrantied.
I can't stress the importance of properly educating yourself before diving in. After all its a couple hundred dollar device in your hand, so you should be well aware of what and how your doing things before just taking a blind leap and then something goes wrong and you come running for help.
Good luck!
Paul
Moderator Team Leader @ Android Central.