how do i delete photos from my iphone that have been synced onto the phone from my computer

Hi there block28,

It sounds like you have synced photos to your device through iTunes, and want to unsync them. This article should help you do that:

Sync photos to your iPhone, iPad, and iPod touch in iTunes

Delete synced photos

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.

If you had moved the photos or deleted them from the computer then this article will help you remove them from your device:

Delete photos and video synced from iTunes when you can’t access the originals

Thank you for using Apple Support Communities.

Cheers,

Sterling