In a large stock pot over high heat, brown roast on all sides. Reduce heat to medium low and add the diced tomatoes with green chile peppers, yellow onion, garlic powder, ground cumin and chili seasoning mix. Cover and simmer until meat comes apart easily, about 3 to 4 hours.
Meanwhile, rinse the pinto beans and soak them in a bowl of warm water.
Remove cooked roast from the pot and set aside. Rinse the pinto beans and pour them into the pot. Pour in enough water to cover the beans and bring to a boil. Cover and simmer until the beans are very tender, about 1 1/2 hours, adding extra water as needed.
Shred roast with fork and discard the fat. Add the shredded meat to the cooked beans and pour in enough water to cover. Cover and simmer for 30 minutes