How to delete photos from an iphone that were imported from a Mac?

I added a photo album to my iPhone from my mac through iTunes a while ago and I'm not sure how to delete it now. I've read of going back to iTunes and unchecking the album that I don't want in my phone anymore, however I deleted that album from my mac too.

Is there any other way to delete this album? It doesn't give me a delete option on the phone so I'm not sure what else I can do. It's taking up some of my space and I don't need those pictures anymore.

You can use a 3rd party software like this iPhone file manager, it can work as an iTunes alternative to delete photos from your iPhone. Hope it helps you.