^^ This. ^^
The game was only intended to utilize one ring, presumably to avoid OP balance issues right out of the gate. Once the Creation Kit is released, expect a mod that will allow 2 or more to be equipped at once.
Through clever enchanting, I was able to create an invincible character in Oblivion using only 2 rings, and a sword/shield (as well as armor obviously). I could literally stand next to an enemy of any kind and take virtually no damage. I did this with both light and heavy armor, and was very amusing.