Short answer : no Long answer : Rooting -- if successful -- does n't change

Short answer: no Long answer: Rooting -- if successful -- doesn't change any of your data, it just gives you root access. Now, if you reflash your phone's ROM -- something you can only do with root access -- then, yeah, you might lose stuff. A lot of people automatically associate rooting with switching ROMs, since rooting is required. But you can root, and then do nothing, if you want. I'm so lazy, I rooted and installed a screenshot app; but it was so worth it. [Okay, not lazy -- I just don't have the need nor desire for much else, at the moment. But if I want to, I can.] Caveat: anything done really, really wrong can screw things up. See: Are there any risks to rooting a device?