Latest firmware update for the Samsung Galaxy Grand Quattro is now available via OTA (over the air), but you have rooted your phone, you will loose it after the update has completed. However, there is a way by which you will be able to preserve the root and still get your Grand Quattro to get updated successfully. All of these steps should be followed before hitting the update button.
Fire up Super Su app on your phone and select OTA survival mode. After that, download and install the update. This will make sure that Super SU file is not deleted, and it still has access to root. Your phone will feel a bit laggy after the update for the first five minutes, so do not fret. It will soon feel faster and smoother than previous firmwares.