So nothing obviously like Exquisite Blood + Sanguine Bond or Earthcraft + Squirrel Nest , but something like Cathars' Crusade and Doubling Season is just fine
A good cooperative game is not one that you will win each time, since there is no struggle involved
While I could extoll the virtues of having access to the best colors for blink effects when building a Roon deck, or the ability to use them to blink powerhouses like Avenger of Zendikar, Craterhoof Behemoth, or Eternal Witness, Roon actually has a much more sinister claim to fame thanks to the rules change involving death triggers in 2020
Since these spells are almost always useful, no matter how much mana you put in, this deck should play remarkably smoothly
He's also the only one who knows the location of the entrance to the Below, where Valgavoth's lair is located