"Everything you could ever want!"
Memes aside, this ring really has everything you could ever want (specifically health, stamina, and vitality).
RoF +2 reaches 161 stamina at 35 endurance, passing the 160 softcap and saving you 5 points (6 points if you have the RoF +3 version).
RoF +2 with LifeR +3 breaks the normal health cap at 40 vigor (same with RoF +3).
And of course vitality, the bonus and gets higher the more points invested.
Probably the most important part is no drawbacks (other than taking up a ring slot).