I travel to NC a week a month from Ohio. My employer is a NC based company but I am able to work from any where - Do I need to file a NC state return even with my emploer withhold my resident state tax?
Yes, but "nobody" does.
12 weeks in NC, every year, on a regular schedule, makes it more likely that you should file an NC return than the average traveling worker.
If you live in a state without an income tax (e.g. FL or TX), it’s more likely you should file in the work states. You can't use the "it all comes out even" rationale for not filing.