Found a fix for that problem
I just re-rooted my phone yesterday (after i bricked my N7105), i would assume the steps are similar.
1. Follow the standard steps to root the phone with Odin.
2. If encounter bootloop, you may have to download the default stock and re-flash the phone to its factory state.
3. After you managed to root the phone, somehow the Knox protection will disable your Super SU. Go to play store, update your Super SU. After the update, run the Super SU. There should be a prompt/popup for you to disable Knox.
4. After step 3, you will be able to install custom rom easily with rom manager =)