If you're looking to make your diesel truck roll coal, there are a few things you'll need to do. First, you'll need to install a smoke stack and exhaust tip. You can find these online or at your local auto parts store. Once you have those installed, you'll need to make sure your engine is running rich by adjusting the fuel injectors. Finally, if everything is set up correctly, revving your engine will cause black sooty smoke to come out of the exhaust and 'roll coal'.