If my opinion matters at all, I'd forego the menu altogether. Instead of the buttons being Open Menu and Attack, I'd have 3 buttons: Attack, Equip Next Die (cycle through them), and Reroll Current Die.
Opening a chest automatically fills up as many dice as you can hold. Because why would you not want to take a die? And your dice are just permanently on the HUD, like in the corner of the screen.
And if you want to get rid of a die, you just press Attack and you'll uselessly throw it away, like throwing away a weapon in Breath of the Wild.
But that's just what I'd do! I don't want to tell you how to make your game.