Duplicating items is a popular trick in Oblivion, and it's quite present in the PlayStation 3 version. Some weapons and armor don't work. The item has to be in perfect health. And the charge on a magic item has to be full too. Here's how you pull it off:
1: Have two or more of the same magic scrolls (they can't be stolen!). If you have three magic scrolls, then instead of duplicating, you will get three copies. If you have four scrolls, you'll have four, and so forth.
2) Click on a scroll twice.
3) Select and drop the item in your inventory that you want to be copied.
4) Leave inventory screen, and you'll find your duplicated items on the floor. Collect them.