Your quoted the error message seems wrong.. the TA partition is in /dev/block/mmcblk0p1
Things to check..
1. USB debugging enabled
2. Whether granted root access to adb shell.. (not terminal emulator).
To check.. connect usb to phone.. Open command prompt in PC.. run "adb shell" (no quotes).. then in that shell run "su".. You should see the root prompt.. (and should see a toast saying superuser access granted). otherwise check SuperSU app to see ADB Shell root access granting status.. maybe denied there.