The Verizon and AT&T Samsung Galaxy S5 isn't the only one to finally obtain root access. The Sony Xperia Z1s on T-mobile has gotten it recently as well. If you subscribe to a T-mobile plan and use the Sony Xperia Z1s then this is likely coming as happy news to you. The Xperia Z1s launched on T-Mobile's network in early 2014, which makes the 6 month waiting period for root access to this device a long one to say the least. The process to do so can be found over at the XDA forum thread from recognized developers jcase and beaups, where you'll find a downloadable zip file that you'll need for the process.
As always with any root for any device you need to have the bootloader unlocked to move forward with the root process, and this is what was apparently hanging people up on achieving the goal of root for the Xperia Z1s in the first place. According to the Xperia Blog, the process to get root for the Xperia Z1s was thanks in part to finding a root exploit for the Sony Xperia Z2 and Sony Xperia Z2 tablet that were released not too long ago, and were announced earlier this year at the end of January during CES. The Sony Xperia Z1s wouldn't be the first device to ever have a longer waiting period before root access could be achieved, and it most likely won't be the last that we'll see either. Although, as we move further and further into the future rooting devices does seem to get easier and easier as a whole. Remember having to root older Android devices like the Mytouch? Not an easy process compared to today's standards.
While root access for the Xperia Z1s is now available, it was mentioned that root exploit is only working and specific to those devices that are using a current kernel, and that it likely won't be possible to use Kit Kat until an Android Kit Kat compatible kernel is posted up for use. Once that time comes, XDA will probably be your best bet at finding a download for it as things often show up here for such things. If you use the Xperia Z1s and are eager to root your device, you can do so by heading to the source link below and following the instructions.