Headspace on the AR is set when the barrel extension is attached to the barrel (i.e. before the retail customer sees the barrel). So assuming the factory set headspace correctly and you are using an in-spec bolt, there is no need to worry about headspace. As a practical matter, every once in awhile, stuff that should be in spec isn't, so a set of headspace gauges to verify that is nice to have.
The only other issue with headspace in ARs may occur when you start swapping bolts between well-worn ARs. In theory, you can create excessive headspace by doing this. In practice, I've seen one case of excessive headspace in 20 years and it was from an improperly set barrel extension on a new barrel.