Board Thread:Dark Souls II/@comment-6431205-20160611183156/@comment-25257440-20160612205440

Denial only stops the loss of health at 1 HP ONCE per cast. Seeing as Denial has only one cast, it would be impossible to continuously stay alive using it. The Ring of Restoration retores health, it does not prevent health from being lost. This means that any health gained from wearing the ring will still be depleted were the player with a strong enough attack (which shouldn't be too hard, since the RoR only restores 3 HP per 1.5 seconds).