How do remove photo files off of your iphone?

Last night i synced my phone and i ended up getting photo files off of my computer that i did not want. And when i went to delete them, it wouldn't let me… So i trying to figure out how to get rid of those photos but keep my original camera roll.anyone know how to fix this without completely loosing everything?

I had a similar problem and the only way i could fix it was by resetting it on itunes, there may be an easier way but thats what i did