How do I delete photos that I accidentally synced from my computer to my iPhone 6?

I plugged my phone into my computer with the intention of syncing my photos FROM my phone TO my computer (as I've done many times before). Somehow I accidentally synced all of the photos from my COMPUTER to my PHONE. Now I'm unable to delete the photos from my phone. I tried to figure out how to delete them from my phone via iTunes, but haven't had any success. Help please!