Remove synced photos

How do you remove photos that were synced to your phone from your computer through Itunes. The photos do not have either the trash can or the trash can is greyed out. When I hook up to computer the photos that were synced do not show on storage. In Itunes with the "sync photos" box unchecked and click on "Sync" a pop up says "Itunes will no longer sync photos to the phone. Do you want to remove or keep photos previously synced to the phone? I click on "remove" it shows it is doing some steps when it is done I check the phone and the photos are still on my phone. I tried it on all folders and selected folders. I have an Iphone 5s. Thank you for any help!!