Apparently, there is a way of updating Android OTA without root removal. You only need an application called FlashFire to keep your root access from being lost when your Android update via Over-the-Air.
2. When you get a notification if your device gets an Android update, download it without installing it.
3. After the update download is complete, go to FlashFire application and this app will automatically detect the update file you downloaded, then press OK.
4. You will go to a page where you can choose what to do when updating your Android system. When you're done, press Flash.
5. There will be a pop-up warning telling you if the update will take some time and the screen will turn black several times. Press OK if you agree.
6. The flashing process will start, and scrolling text will appear on your smartphone screen. But do not worry, it's just a flashing process done by FlashFire.
7. Boom! Your smartphone already has an updated Android system.
However, if you fail to do so, maybe this second way you can also try. Usually your smartphone fails because you've customized the kernel, or /system partition has been modified with Xposed Framework.
The way to keep using FlashFire application, but in a slightly different way. Just follow it!
1. Donwload factory image for your device. For example, you want to flashing Nexus 7, you can search the most recent factory image through this link. Copy factory image with .tgz extension to internal storage or SD Card used by your smartphone.
2. Go to FlashFire, tap menu and select Flash firmware package.
3. Find the factory image you saved earlier, then select it.
4. FlashFire will scan the file you selected earlier to check it.
5. There will be several options that you can do to flashing your device. Choose what you need. If you have, press the check mark at the top right.
6. You will go to the page where there is a list that will be FlashFire when flashing your device. If already checked.
7. If you have checked it, press Flash and go to OK. Your device will be flashing immediately and blank screen will appear several times. Foilaaaa, your Android has been updated.
Well, that's how to update Android OTA without removing root. It's easy?