I use Sony Sketch and I am not rooted. Visit the thread "Fonts for your S3" and download the file to your phone. Then download ES File Explorer from the play store. Then go into it and click the "downloads" folder. Then "fonts zip", then find "Sony Sketch". When you find it, DOUBLE CLICK on it. After you double click, just go into your phone settings and select it in font style.
Your phone has a setting to say that for everything except Google Play. It will even say that for the Amazon Appstore. I have downloaded it on two different S3's without a single problem. I personally wasn't worried, and have had no problems.