If you are using Panda, OpenHome, AHome, those types of home replacements that you can get from the market then no you do not have to be rooted to use the themes. There are a ton of themes that are on the market for download that can be used and look pretty good. Good luck and just a word of advice that my wife learned the hard way, make sure that you read what home replacements the theme you are looking at is compatible with. There are some themes that will only work with specific home replacements.