Q: How do I delete an album from my iPhone that was synced through Photos?

You delete them from the phone by syncing again with different settings. See the following from Sync photos from your computer to your iOS device using iTunes - Apple Support

1. In iTunes, locate and click on your device.
2. Click Photos.
3. Choose "Selected albums" and deselect the albums or collections you want to delete.
   To delete all synced photos, deselect "Sync Photos from" and, when asked, click "Remove photos."
4. Click Apply.

Learn how to delete photos and video synced from iTunes when you can't access the originals.