Bedrock Tortoise

During your turn, creatures you control have hexproof.
Each creature you control with toughness greater than its power assigns combat damage equal to its toughness rather than its power.

Gemstone Mine

This land enters with three mining counters on it.
{T}, Remove a mining counter from this land: Add one mana of any color. If there are no mining counters on this land, sacrifice it.

Rock Hydra

This creature enters with X +1/+1 counters on it.
For each 1 damage that would be dealt to this creature, if it has a +1/+1 counter on it, remove a +1/+1 counter from it and prevent that 1 damage.
{R}: Prevent the next 1 damage that would be dealt to this creature this turn.
{R}{R}{R}: Put a +1/+1 counter on this creature. Activate only during your upkeep.

Boulder Rush

Target creature gets +2/+0 until end of turn. (Then exile this card. You may cast the creature later from exile.)

Rimrock Knight

Rimrock Knight // Boulder Rush

Acolyte Hybrid

Heavy Rock Cutter — Whenever this creature attacks, destroy up to one target artifact. If an artifact is destroyed this way, its controller draws a card.

Rumbling Rockslide

Rumbling Rockslide deals damage to target creature equal to the number of lands you control.

Geology Enthusiast

At the beginning of your end step, create a tapped Powerstone token. (It's an artifact with "{T}: Add {C}. This mana can't be spent to cast a nonartifact spell.")
{6}: Draw a card and put a +1/+1 counter on this creature.

Toggo, Goblin Weaponsmith

Landfall — Whenever a land you control enters, create a colorless Equipment artifact token named Rock with "Equipped creature has '{1}, {T}, Sacrifice Rock: This creature deals 2 damage to any target'" and equip {1}.
Partner (You can have two commanders if both have partner.)

Akki Rockspeaker

Rockslide Sorcerer

Whenever you cast an instant, sorcery, or Wizard spell, this creature deals 1 damage to any target.

Rock Basilisk

Whenever this creature blocks or becomes blocked by a non-Wall creature, destroy that creature at end of combat.

Rock Slide

Rock Slide deals X damage divided as you choose among any number of target attacking or blocking creatures without flying.

Geological Appraiser

When this creature enters, if you cast it, discover 3. (Exile cards from the top of your library until you exile a nonland card with mana value 3 or less. Cast it without paying its mana cost or put it into your hand. Put the rest on the bottom in a random order.)

Rockfall Vale

This land enters tapped unless you control two or more other lands.
{T}: Add {R} or {G}.

Spinerock Knoll

Hideaway 4 (When this land enters, look at the top four cards of your library, exile one face down, then put the rest on the bottom in a random order.)
This land enters tapped.
{T}: Add {R}.
{R}, {T}: You may play the exiled card without paying its mana cost if an opponent was dealt 7 or more damage this turn.