How to root ASUS ROG Phone 3
1. Patched boot.img
2. ASUS usb drivers (https://www.asus.com/Phone/ROG-Phone-3/HelpDesk_Download/)
3. Magisk manager (https://magiskmanager.com/downloading-magisk-manager)
4. Platform tools (https://dl.google.com/android/repository/platform-tools-latest-windows.zip)
✅ How to root
After unlocking the bootloader using this guide we need to extract the boot.img for your exact firmware from the link given on number 1. Meaning the link embedded in the patched boot.img is not the actual link to download a boot.img rather it is the latest stock rom downloader for ROG 3 so that anyone could download and extract the stock boot.img from the rom provided! But it is a must thing to make sure that your phone's build is exactly alike with the latest stock rom provided or u must flash this rom before using its boot image as an input for the next guide.
After having the boot.img from the rom we need to patch this image file using magisk manager(3).
1. Make sure you have stable internet connection on the phone.
2. Send the boot.img to internal storage.
3. Install magisk manager (make sure you download the latest version 8.0.2 from the official site)
4. Select install on the magisk then don't tick any boxes or if you see one untick it and tap next
5. In the "method" part choose "select and patch a file"
6. browse to the .img file you copied earlier to the phone and give it!
Once the boot.img is patched send the Magisk_patched.img from internal storage to your pc.
Now download platform tools(4) and extract it. Rename the magisk_patched.img to boot.img and copy the file to the root folder of the extracted platform tools!
Finally To flash the image open the platform tools folder then right click on an open space while holding shift key. Click on "open command windows here" and type the following cmd while the phone is connected in bootloader mode!
1. fastboot flash boot boot.img
2. fastboot reboot
Done! Your phone has now a systemless root!