The T-Mobile version of the Samsung Galaxy S2 sports a Qualcomm processor instead of the Exynos SoC found in other variants. Like all other Galaxy S II variants, users would need to use ODIN to get root access to their handset.

Below are the steps to root the T-Mobile variant of the Samsung Galaxy S II-:

1. First and foremost, users need to download ODIN and the required drivers. Both the files can be downloaded from here and here, respectively. If you already have KIES installed, then you don’t need to install the required drivers.
2. Download Clockworkmod (CWM) Recovery from here, which you are going to flash via ODIN. Also download Superuser and its binary file, which you need to flash later on via CWM from here.
3. Fire up ODIN on your PC. Then boot your T-Mobile Galaxy S II in Download Mode. To do so, switch off the phone and re-insert the battery. Then press the Volume Up + Volume Down button simultaneously. Your phone will then boot into Download mode.
4. Now connect your phone to PC. When ODIN detects it, a random COM number will be display, which will be glowing in yellow.
5. Press the PDA button, and then select the ClockworkMod Recovery which you downloaded in Step 2. Press the Flash button and wait for ODIN to flash the file.
6. Once the file is flashed, your phone will automatically reboot. Now, transfer the Superuser and SU file to your phone, and switch it (phone) off.
7. Now, you need to boot your phone into recovery mode. Press the Volume Up + Volume Down + Power button simultaneously to do so.
8. Once your phone boots into CWM, navigate to the ‘Install Zip from Sdcard’ option using the volume keys and select the Superuser+SU file which you transferred to your phone in Step 6.
9. Once the file is flashed, reboot your phone. You have now successfully gained root access to your phone!