At the beginning of your end step, each player exiles the top card of their library. Until your next end step, each player may play the card they exiled this way.
Whenever a player plays a land from exile or casts a spell from exile, you put a +1/+1 counter on target creature and create a Food token. (It's an artifact with ", , Sacrifice this token: You gain 3 life.")
Rocco turns your end step into a group-wide impulse draw engine, exiling the top card of every library and letting everyone play it until your next end step. You profit hardest because every land or spell played from exile (by anyone) puts a +1/+1 counter on a creature you choose and makes a Food. Snowball those counters and Food onto a threat or sacrifice engine, then close before the table catches up on the symmetrical card advantage.
Generates value and counters off opponents' plays too, not just your own
Steady stream of Food tokens fuels lifegain, sacrifice, and artifact synergies
Cheap three-mana commander that immediately advances the board
Plays well into +1/+1 counter and big-creature strategies in Naya
The exile draw is symmetrical and can hand opponents free gas
Triggers only on your end step, so it's slow without ways to play extra cards
Relies on a target creature being present to bank counters
Vulnerable to removal of Rocco himself, which shuts off the engine
No built-in evasion or protection for your counter-stacked threat
Another impulse-style payoff that snowballs with Rocco's card flow.
Add ways to play extra cards each turn (extra land drops, cascade, flash) so you exploit the impulse window before opponents do, and stack counter payoffs like Cathars' Crusade and The Ozolith to convert Rocco triggers into a winning board. Tighten the mana base with fast Naya rocks and fetch/dual lands, then add a decisive finisher such as Craterhoof Behemoth or Triumph of the Hordes so the snowball actually closes games.