Commander (1)
1x Roon of the Hidden Realm
Creature (34)
1x Acidic Slime
1x AEther Adept
1x Agent of Treachery
1x Altered Ego
1x Angel of Condemnation
1x Brago, King Eternal
1x Bramble Sovereign
1x Brutalizer Exarch
1x Coiling Oracle
1x Deadeye Navigator
1x Duplicant
1x Eternal Witness
1x Farhaven Elf
1x Flickerwisp
1x Gilded Drake
1x Hornet Queen
1x Lavinia of the Tenth
1x Manglehorn
1x Meteor Golem
1x Mistmeadow Witch
1x Phyrexian Ingester
1x Prime Speaker Zegana
1x Risen Reef
1x Reflector Mage
1x Restoration Angel
1x Riftwing Cloudskate
1x Seedborn Muse
1x Solemn Simulacrum
1x Soulherder
1x Stonehorn Dignitary
1x Thassa, God of the Sea
1x Vedalken Plotter
1x Venser, Shaper Savant
1x Woodfall Primus
Land (31)
1x Arid Mesa
1x Command Tower
1x Flooded Strand
4x Forest
1x Glacial Fortress
9x Island
1x Lumbering Falls
1x Misty Rainforest
1x Path of Ancestry
3x Plains
1x Polluted Delta
1x Reliquary Tower
1x Savannah
1x Scalding Tarn
1x Seaside Citadel
1x Tropical Island
1x Tundra
1x Wooded Foothills
Instant (10)
1x Cyclonic Rift
1x Eerie Interlude
1x Force of Will
1x Ghostway
1x Illusionist's Stratagem
1x Momentary Blink
1x Pull from Tomorrow
1x Radiant Purge
1x Return to Dust
1x Sphinx's Revelation
Enchantment (1)
1x Aura Shards
Planeswalker (1)
1x Venser, the Sojourner
Artifact (16)
1x Commander's Sphere
1x Conjurer's Closet
1x Darksteel Ingot
1x Everflowing Chalice
1x Illusionist's Bracers
1x Lightning Greaves
1x Mind Stone
1x Obelisk of Bant
1x Panharmonicon
1x Pristine Talisman
1x Sol Ring
1x Swiftfoot Boots
1x Talisman of Progress
1x Talisman of Unity
1x Thran Dynamo
1x Vedalken Orrery
Sorcery (5)
1x Braingeyser
1x Explosive Vegetation
1x Mind Spring
1x Skyshroud Claim
1x Traverse the Outlands
Bounce based control deck. Ramp up to as much mana as you can early on, you will need it. Roon is a mana hungry deck. Be sure to play as much lands as possible by bouncing Risen Reef, Coiling Oracle, Farhaven Elf, and Solemn Simulacrum. Traverse the Outlands should be cast for at least four lands, preferably more than five.
Once you have enough mana to work with, start casting and bouncing board disruption ETB Creatures like Manglehorn, Lavinia of the Tenth, Phyrexian Ingester, Duplicant or Meteor Golem. Try to keep Roon of the Hidden Realm protected with Hexproof equipment if possible. Manage your resources, draw spells, and bounce effects to make sure you always have a full hand of cards and that mana is available to bounce creatures in response to removal.
Once you have enough pieces out like Panharmonicon, Conjurer's Closet, Seedborn Muse, or Brago, King Eternal, you can begin to soft lock players into not being able to advance their boardstate. Re-use ETB effects as many times as you can. Venser, Shaper Savant becomes a re-usable bounce and counterspell. Gilded Drake will return to the battlefield under your control when bounced and will retrigger. Vedalken Plotter can be used to steal powerful lands or simply disrupt an opponents mana base by locking them out of a color.
Bouncing any of these creatures enough times will usually result in a hard lock / win: Brutalizer Exarch, Woodfall Primus, Acidic Slime, Woodfall Primus, Riftwing Cloudskate, or Agent of Treachery. Deadeye Navigator should usually be saved until you have enough mana to pay for multiple triggers on the same turn you cast it.
If you can't establish a lock with the bounce effects, chip away at your opponents health with any creatures you can. Roon of the Hidden Realm can make an excellent attacker and has both Vigilance and Trample. Learn the nuances of Roon's tap ability for bouncing creatures out of combat or bouncing them in response to a removal effects.