After you bring rock roast to Cooke at Bedrock Bistro, he asks you to bring any more you find.
Quest Location
To start this quest, first you have to complete Meat for Meat. You may also need to complete the Fire Temple. Then talk to Cooke to start this quest.
How to Complete the Quest
You can find rock roast in East Restaurant Cave and other locations.
You should only bring one rock roast at a time, because any others that you attach to the mine cart will disappear when you give one to Cooke.
Pick up the rock roast and carry it to Cooke, and there will be a cutscene.
Quest Reward
Cooke gives you Seared Gourmet Steak.