The update process patches files. It, expects files to be the original. Typically rooting alone will not cause update to fail but if you have modified/deleted files, that could cause the update to fail.
The process I have given is for updating to the latest without losing data. For each step, you just need the update file. Dont worry about the thread.
You do not have to worry about retaining root as the latest update, NC1, is rootable with towelroot.
If you dont ming losing data (about having to reinstall apps and redo settings), then you can directly odin flash the stock NB1 firmware and then OTA update to NC1.
Stock NB1 firmware and steps are available in
All Thing AT&T thread.