Gaining root on the US Galaxy S III variants isn’t that difficult, with the possible exception of the Verizon variant. However, the typical root method uses Odin, which means two things. The first is tripping the flash counter, and the second is a garish yellow triangle. Well, for the T-Mobile/Wind/Moblicity Samsung Galaxy S III, root and custom recovery is now achievable without affecting the counter or getting that horrible yellow triangle.
As expected, the method does require a bit more than the standard rooting method. The guide, written by XDA Senior Member mrRobinson actually still uses Odin but doesn’t trip the flash counter. What’s more interesting, it only uses a single file from a rooted stock system image calledroot66. Sadly, this means that users have to download the entire half a GB system image in order to get it.
Aside from that, the process is pretty simple. Download the rooted system image, extract theroot66 tar file, flash it over Odin with Auto Restart and F Time Reset checked. This will root the device. After that, mrRobinson links to a thread that will help users install a custom recovery so that the counter still doesn’t get tripped.
For the full method and download links, check out the original thread.