Plug-in your USB cable.
Wait for iTunes software to open automatically by itself.
Click on your device.
Now, click on the “Photos” tab.
Check the selected Photo folder on your computer.
Open the sync photo directory on your computer(if you have forgotten, just click “Choose Folder” and it will prompt you to the location). Delete the custom made photo folder on your computer(don’t remove “iPhone/iPod Photo Cache” folder).
Click on “Apply” button at the bottom right corner to start syncing your iPhone.
All the deleted photo albums on your computer just now, are removed from your iPhone.
Hope this helps!