How to remove synced photos on iPhone

Okay I have a few steps that may be you can try:
The First one is.
 1. Make a new folder
      Name it what you like. You can also use your old folder. Just make sure it is an empty folder.
 2. Insert your device
 3. Open iTunes
 4. Select your device, go to the photos
 5. Sync photos from your new folder.

The Second one is.
 1. Insert your device and then open iTunes
 2. Select your device, go to the photos
 3. Simply uncheck the check box of "Sync photos from"
 4. And then you will get option to Don't Remove Photos or Remove Photos. Of course, I will recommend          you to click Remove Photos
 5. When you click apply the photos all the synced photos will be deleted

*Please not that these step will delete all of your synced photos from the library. Please make a backup if you still want to keep some of your Photos.