IPhone 4's how do you remove pictures?

So i plugged my iphone into the computer and i had done something to sync my photos and everything. And now the photos i had in my laptop are all in my photos, how do i remove my photo library and the albums it had made? Cause it won't let me like delete them or anything on my phone.

And no, I don't even have iCloud or photostream etc.

Ok, so like, um, where do you, like, want to remove, like, your photos, you know, from? Like your phone, right? But not your computer? Because the whole point is to have them on, like, both, you know?