Themes (icons and wallpapers) don't need root. Just use a launcher that will use the theme you want. (Look in the theme's description - it'll tell you that it works with Nova, Apex, Go, etc. Use one of those launchers. [A launcher is just an app, you don't need root to install one.])
Fonts? I've never found a need for changing them, so I can't do anything but guess, and I won't.
You can also look up the LG World app. That's what I have on mine. I got some good fonts from it. Just make sure you download the apk from the LG website.
http://forum.xda-developers.com/showthread.php?t=2460461 they have a lot of good themes compiled here and don't need to download a 3rd party launcher if you don't want. Just download the apk you want and install it then go to. settings -> home screen -> theme. And select it from there.