The US carrier versions ship with locked bootloaders, but the Exynos ones got rootFret not, however, as T-Mobile's flamboyant CEO John Legere would try and come to the rescue, and has apparently ordered his engineers to probe Samsung on workaround solutions that will satisfy all parties involved. He is not doing this only from the good of his own heart, though, as some users have reportedly started returning their phones with locked bootloaders, seeing that there will be no modding development for a while.
@MarkHibbard1 I'm aware some are upset. It's under Samsung’s control, but my engineers are asking them for a solution that they can support.— John Legere (@JohnLegere) March 13 2016
For comparison, the international Galaxy S7 and S7 edge versions, powered by Samsung's own Exynos chip, have no such restrictions, and already got root and TWRP recovery installed.
Here's what you need to do if you have one of those and want it rooted - as usual, make sure that you have the correct model (an Exynos one), be advised that rooting will trip KNOX, back up everything beforehand, and charge your phone before you proceed:
1.Tap on the phone's build number in Settings > About five times to enable Developer options;
2. Go to the Developer settings and enable "OEM Unlock";
3. Get Samsung's Odin and Chainfire's auto-root file for your respective device on your computer:
4. Unzip the files and get the “.tar.md5” extension;
5. Hold Home, Power and Volume Down buttons for a few seconds on your Galaxy S7 or S7 edge to go into the download mode;
6. Download and install Samsung's Mobile Phone Drivers so that Odin can find your phone;
7. Run Odin on your computer, and connect the phone to it with the USB cable, while it's in download mode, until Odin shows “Added message”;
8. Click the AP button in Odin, and select the .tar.md5 file you unzipped in step 4;
9. Click START and enjoy the ride. Your Galaxy S7 or S7 edge won't show progress, just the S7 logo while the process is ongoing. It will reboot a couple of times, and then will boot into Android.