These spicy chuck roast tacos are a great way to switch up your taco night routine. Using a food processor, blend together chili powder, cumin, paprika, garlic, and salt to create a spice rub. Rub the mixture all over the chuck roast and sear it in a hot skillet until browned on all sides. Transfer the roast to a slow cooker and add diced tomatoes, onions, and jalapenos. Cook on low for 8 hours. Shred the meat and serve in warm tortillas with your favorite taco toppings.