| Baelin |
Wraithstrike's first statement is correct. You gain the magical benefits of only up to two magical rings-no matter where you wear them on your body. (Jokes about magical earrings and genital piercings abound are normal in the community. Characters wishing to keep their rings hidden can wear them on their toes as well if so desired.)
You can wear two rings of any kind on the same hand and gain the benefits of both, but no more than that.
http://paizo.com/pathfinderRPG/prd/magicItems/rings.html wrote:
"A character can only effectively wear two magic rings. A third magic ring doesn't work if the wearer is already wearing two magic rings."
Assuming you have two Rings of Counterspell loaded respectively with a spell of Fireball and Magic Missile, the rings would automatically trigger to counter either one.