Google account creation or login is not mandatory after a factory reset, and performing a factory reset in either the stock or custom recovery does not need a Google account either.*
A Google account can be set up/connected any time after skipping that step by starting the Play Store app.
To do any initial customizations following a factory reset (even without a Google account credential) though, you will need to connect to a WiFi AP.**
* something to watch out for is if your root app is not installed as a system app but as a market app - a factory reset will delete app portion, so restoring the app portion will either require a sideload (of a backup of the) .apk, or a google account to download it again from the market.
** perversely, the WiFi router does not need to be connected to the internet; after the tablet is connected to a router , the WiFi setup screen on the tablet will eventually time out and let you continue. This suggests a means to partially configure a tablet following a factory reset without the tablet ever "phoning home".
Edit: From your post it is not evident whether you are planning (i) a factory stock install followed by re-rooting, or (ii) have a lightly-rooted stock that you merely want to perform a factory reset on. In either event a solution would be to make sure that SuperSU is installed as a system app. That way 100% of your root kit will survive a "factory reset" procedure in the recovery. In the case of (i) you can certainly reconnect to your own Google account to download the newest version of SuperSU, get it installed as a system app (I think that is a menu item in the SuperSU app), and then do a "factory reset" afterward.