A very simplified version would be this.

Ring of uncanny defense Rare, requires attunement

Once per long rest, when you are hit by an attack that is not a critical hit while wearing this ring, you may use your reaction to cause that attack to miss and all future attack rolls that are equal to the first roll also miss. This benefit lasts until you finish a long rest.

This is a little stronger as it comes with an automatic damage negation, but it guarantees it will see use once per day if you use it. It also negates rolling dice which consumes a deceptively long amount of time if you introduce a lot of effects that do this

Currently it seems to specify that you roll the 1d10+5 when you attune. If you know that your average enemy has a +5 to hit, the tactically smart choice is to keep re-attuning until you get a 15. However if you move that to be triggered as a reaction, then the tactical playoff is still waiting for a common value to come up but also potentially choosing to negate a dangerous hit on an attack that's unlikely to come back up like a 28 is a alternative tactical option.