You learn from your friend that the Oreburgh Gym Leader, Roark, has gone to the mine, so you go to look for him there.

Get an X Defense

To the right of the entrance, there is an X Defense.

Catch Pokémon

In the cave, you can catch Geodude, Onix, and Zubat.

Battle Worker Mason

Go south to the next part of the mine. Go east and talk to the second miner and you will battle Worker Mason. He has a level 9 Machop. You get 648 Pokédollars for winning.

Get a Potion

South of the worker, you find a Potion.

Battle Worker Colin

In the southwest of the area, you can talk to the worker to battle Worker Colin. He has a level 7 Geodude and a level 7 Onix. You get 560 Pokédollars for winning.

Get an Escape Rope

West of the worker, you find an Escape Rope.

Talk to Roark

Go back to the middle of the southern part of the area and talk to the red-haired person. This is Roark. After you talk to him, he will go back to the gym.

Return to the Gym

Now you need to return to the Oreburgh Gym. You can either use the Escape Rope that you just got, or you can go the long way if you want more chances to catch pokémon. Stop in at the Pokémon Center, then enter the Oreburgh Gym.