Most of the time I see it remove all the installed apps, wipe the data and set the settings to defaults. Being rooted is not helping here as a rooted phone could have some other OS image installed and change what the reset does.
So until the folk that did the root job tell you what will happen, it's only a guess.
I rooted my T-Mobile Samsung SGH-T679 but some apps like Email and Google Play Store don't work anymore (Sorry! Force Close) but other apps do work. I am considering to Factory Reset the phone and start new but a Google search on this isn't really clear on this procedure. Since this is a programmed T-Mobile phone does the hard reset return to the T-Mobile settings/apps as purchased and I lose my rooted status? Or does it really mean that everything will be deleted and I can start anew and reload only the apps I want?