Roon was my first real commander deck, and I've been tweaking and occasionally revamping it ever since. At first, cards such as Sphinx of Uthuun had a place in the deck, while essentials such as Cultivate were absent. As a result, The deck was slow and clunky, but nonetheless fun to play. As I've grown as a Magic player, this deck in particular has really grown with me, with the current version arising at the time of the mulligan rule change to be far less greedy and more consistent.
Depending on cards in hand, there are two distinct ways to play this build. The first is when your hand has no instant speed tutors. In that case, you play it as a midrange deck, getting solid, consistent value from each card in your hand, while being careful not to overextend into possible sweepers, or holding an Eerie Interlude to play around that. With this hand, one of the best value plays is to evoke a Mulldrifter, and with the evoke trigger on the stack, exile it with Roon, Eldrazi Displacer, or Mistmeadow Witch. This draws 4 cards and leaves you with a Mulldrifter ready to be blinked further. Your hand will likely be full for the rest of the game after that, eventually moving into the second playstyle.
The second playstyle arises once Chord of Calling is in hand. In this case, the deck can start to play whatever role it needs to. To enable this, tutor for Eternal Witness, getting back the tutor from your graveyard. From there, every turn cycle is a matter of passing on your own turn, tutoring up an answer to whatever threatens to kill you, and then blinking Witness to set it up again. Ultimately, once every other player is reasonably tapped out or you're threatened with lethal, tutor up Peregrine Drake + Eldrazi Displacer/Deadeye Navigator to enable infinite mana. With infinite mana, tutor for Mulldrifter to draw your whole deck, Venser, Shaper Savant to bounce every opponents' permanents, or Avenger of Zendikar + Craterhoof Behemoth to swing for lethal.
Card Packages
Roon Redundancy
-Venser, the Sojourner: Only exiles permanents you own, but can be tricky, exiling mana rocks or lands to bring them back untapped at the end step. Venser's minus is mostly used to attack and kill opposing planeswalkers, but occasionally allows for a lethal alpha strike. The ultimate is obviously game winning.
-Eldrazi Displacer: Super powerful card, provided colorless mana is present. Colorless mana can be found fairly consistently through basic land fetchers fetching Wastes, several mana rocks, utility lands, and the trinket mage package. Unlike some of the other blinkers, Displacer brings the creature back instantly, allowing for multiple triggers that get out of hand quickly. However, that also means Displacer won't save any creatures from board wipes. Displacer can be the tap down opposing attackers or blockers, but be careful of those with their own enter/leave abilities.
Brago, King Eternal: Blinks your entire board, which oftentimes is absurd. Triggers enter/leave effects, untaps mana rocks, gives creatures pseudo-vigilance. Wonderful card.
Eerie Interlude: Much like Brago, blinks all your creatures, and turns board wipes into Plague Wind.
Trinket Mage
Sol Ring: One of the most powerful cards in the format. Usually the first thing to get off of Trinket Mage, in the early or midgame.
Expedition Map: Very versatile card to find off Trinket Mage. Searches for colorless lands to enable Eldrazi Displacer, or finds for mana-fixing lands. However, if colors are fine, either Reliquary Tower or Alchemist's Refuge are the lands to grab. The deck often draws a lot of cards, and Reliquary Tower is critical. Alchemist's Refuge, on the other hand, lets you to start to play at instant speed, which is fantastic. Usually the second search off of Trinket Mage, unless Sol Ring mana is irrelevant, in which case it depends on board presence and hand composition to determine whether an Alchemist's Refuge/Reliquary Tower is better than a Sensei's Divining Top.
Sensei's Divining Top: Excellent card filtering with the amount of shuffle effects in the deck. Smooths draws, and sometimes enables Hail Mary tap + draw Counterspell shenanigans. Usually the last Trinket Mage target.
Unorthodox Choices
Kiora, Master of the Depths: Kiora's abilities synergize wonderfully with everything the deck wants to do. Plussing her untaps a land and a creature, giving some marginal ramp and usually untapping Roon to give another activation. Alternatively, untaps a different creature to play defense if Roon is off the battlefield. Her minus is a fairly consistent draw 2, helping to hit land drops and plenty of gas, while additionally putting the rest in the graveyard for Reveillark and Sun Titan shenanigans. Her ultimate is obviously plenty of value, but not game-winning in the way that Venser, the Sojourner's ultimate is.
Perplexing Chimera: Perhaps not that unorthodox, as I've seen it in a decent amount of other lists, but it can seem strange at a glance. Ideally, the card is played while you have Roon out, allowing you to steal a spell, bounce the Chimera with Roon, and return it to your control. However, I've been fairly happy playing it without Roon, as it results in a panic. Sometimes, the game slows to a crawl as no one plays spells out of fear of having them stolen, which is perfect. Other times, it forces an early board wipe. Alternatively, players ignore it, and give you a free Keranos, or allow you to redirect a Mind Twist back at its controller. While initially I thought of cutting Chimera, it's been wonderful in practice.
Stonecloaker: While Angel of Finality is often the more powerful card, Stonecloaker acts as a great alternative with its native flash. Interrupts Time Warp + Archaeomancer combos and reanimation, but won't do much versus Rise of the Dark Realms or Living Death. Stonecloaker also has the upside of returning a creature you control to your hand to recast it again for more value. Can return itself if Angel of Finality can't be found, to repeatedly snipe a Meren of Clan Nel Toth target, for example. Great value card, although it's a bit of a concession to my playgroup's graveyard emphasis, certainly not an essential card, but one I'm very happy running.
Notable Exclusions
Solemn Simulacrum: Usually considered an EDH staple, and by all means it's decent. However, in most green decks I find him to be super mediocre. For four mana it doesn't do enough, and I never find myself wanting to use a blink on Simulacrum. I'm a lot happier with Cultivate,Kodama's Reach, and Wood Elves.
Rite of Replication: In many decks, this can be a great way to win. Here, there aren't enough solid proactive plays with it. Sure, it's alright with Acidic Slime or Terastodon, but outside of those, the creatures are too situational, and I'd rather not rely on opponents to get value.
Reflector Mage: Too low impact to be worth a card slot, being only creatures.
Tamiyo, Field Researcher: While similar to Kiora, Master of the Depths, (drawing 2 cards off an activation), but often relies on opponents to get value, without additionally fueling graveyard synergies. The minus is pretty mediocre, not much else to say.
