Camera roll will ALWAYS be there. It is temporary storage for ALL pics taken with iphone
Photo Library will ALWAYS be there. ALL photos synced to iphone are in this album. Thos exact same photos can also be accessed from the albums which you synced, just as a song is in your library and in a playlist, and a book is in the public library and in the fiction section.
This is how Apple handles photos.
This is a long round about way to delete photo albums from iphone. I have iPhone 4s and have a windows 7 pc.
I made a new folder on my desktop and named it "photos from computer". Then I opened My Pictures folder on my computer, copied all the photos I wanted to move to my iphone and put them into this new folder on my desktop.
Plug your phone into your computer. When syncing photos from your computer to your iphone, it will create a new album on your iphone. ("photos from computer" and photo library.)
First, you need to save any photos from these 2 new albums to your camera roll.
Open photo library (or any other photo album created that you want deleted). Click on a photo, click edit, I clicked on the magic wand on the bottom just to make some sort of edit to the photo, click save and save photo to camera roll. Do this for EVERY PHOTO you want to save.
Open itunes. Click on your device in the left hand column. Click on the photos tab. Choose Sync photos from...
Choose All folders, Click Sync.
Click on the box with the check mark in it next to Sync photos from.
A message box will open that says: "itunes will no longer sync photos to the iphone (your named phone). Do you want to keep or remove photos previously synced to your iphone?"
Select Remove photos.
Click on Apply.
The next time you plug your iphone into your computer, open itunes and you will be able to sync from your iphone again.
This is a lengthy process BUT IT WORKS.
connect you iphone to itunes, select your iphone in the left column, then go to PHOTOS, check SYNC photos from, then check SELECTED folders, if you don't check any folder all folders will be deleted from your iphone, of course you can keep the ones you want. CLICK on APPLY. You are done! Of course you can go back later and all your folders should be on your computer. Check the folder(s) you want in your iphone and click on "apply" again, easy,,,