Prep Chuck Roast: Bring your roast up to room temperature by allowing it to sit on the counter for an hour before cooking it, trim fat if there is an excess, most will render during cook, but if it more than 1/4 inch thick, trim it to help it cook faster.
Season Chuck Roast: In a small bowl mix together spice rub ingredients, then using a brush, brush olive oil over the surface of the chuck roast, and evenly coat with the spice rub.
Prepare Pellet Smoker: Set your smoker temp to 250 degrees F. And turn it on. Leave lid open when igniting. Once smoke is coming out of the smoker, close the lid, and allow to preheat for a minimum of 15 minutes.
Cook Chuck Roast: Place chuck roast directly on the grates, and insert a probe or thermometer into the thickest part so you can monitor the cook progress. Depending on the size of the chuck roast, it will take about 7-9 hours to fully cook. This time will vary based on outdoor temperature, consistency of heat with your smoker, humidity, the fat content of the chuck you purchased, as well as whether or not is is bone-in or boneless. So keep an eye on it, and use a thermometer. Cook until it reaches an internal temperature between 197 degrees F and 203 degrees F. If you pull it off sooner it will not be nearly as tender.
Rest the Roast: Once your chuck roast reaches temp, double check it with an instant read thermometer, like the Thermapen One, and then remove from the grill. Let it rest in a foil pan, tented with foil for 20-30 minutes to allow juices to redistribute, and the meat to become fully tender.
Prepare Other Ingredients: While your roast rests, it is time to prep the other ingredients for your tacos. Char your tortillas, mix up your crema, guac, salsa, etc, and any of the other toppings you want for your chuck roast tacos.
Shred the Chuck: Once you have rested the meat, it is time to shred. If you bought a bone in roast, remove the bone and use forks, or shredding claws to shred the meat. It should be tender and easy to shred.
Assemble Tacos: Assemble with some of the shredded chuck roast, and whatever toppings you like best. Enjoy!