Use a sharp knife to trim excess fat from the chuck roast, leaving a thin layer for flavor and moisture.
Thoroughly pat dry with paper towels, then rub a thin layer of mustard all over the chuck roast. Worcestershire sauce works just as well.
In a bowl, mix paprika, ground pepper, garlic powder, onion powder, mustard powder, dried oregano, cumin, cayenne pepper, kosher salt, and brown sugar (if using). Mix well so the ingredients are evenly distributed.
Season the chuck roast with salt. Then, evenly coat all sides with the rub, pressing down so it sticks.
Tightly cover and let rest in the fridge for at least an hour or preferably overnight for optimal flavor.
When ready to smoke, remove it from the fridge and let it rest on the counter while you prep the smoker.
Preheat your smoker to 225-250°F (follow the manufacturer's instructions for your specific smoker).
Select the wood pellets of your choice (I used the competition blend).
Place the chuck roast in the smoker, and smoke for approximately 4-5 hours, or until the roast's internal temperature is between 165-170℉ (72-76℃) and it has developed a good bark (flavorful crust that forms on the roast's surface).
Remove it from the smoker and tightly wrap it with butcher paper or foil. Place the wrapped chuck roast back in the smoker and continue smoking until the internal temperature is around 205°F (95℃).
Remove and let it rest for about 30-60 minutes to allow the juices to redistribute throughout the meat and the fibers to relax for a more tender and juicy chuck roast. Please don't skip this step.