How to multiply items in Oblivion. Duplication glitch.

You'll need two different types of scroll and at least two of one of the types.

Then just select the one you have more of and drop the other.
You can keep doing this until you have ridiculous amounts of items though dropping too many could cause the game to crash.

Hopefully I've explained myself properly, but if not ask me to explain further in the comments.

Then to quote Lieutenant Rasczak "Have fun, that's an order"