Place the roast, onion, bay leaf, garlic, water, tomatoes, chilies, salt, peppercorn, and carrots in a large stock pan and bring to a rolling boil. Cover with a tight lid and lower heat to medium. Let simmer 1½ hours.
Add the potatoes, cover, and cook another 1½ hours.
Remove the meat and potatoes and set aside to cool slightly.
Strain the broth into a saucepan. Puree the veggies that are left in the strainer in a food processor and add back to the saucepan. Bring back to a low boil over a medium-high heat and cook down allowing the flavors to intensify and the broth to thicken.
Meanwhile, mash the potatoes with the refried beans. Shred the beef and stir into the bean mixture.
Using tongs, dip the tortillas in the sauce to prevent breakage.
Scoop 2 tablespoons beef mixture onto the left side of the tortilla. Roll into a tight roll and secure with a toothpick. Repeat for all the tortillas until done.
Heat 1-inch of oil in a heavy skillet to 350°F. Working in batches carefully add a few taquitos to the hot oil and fry about 1 – 2 minutes, or until golden brown. Drain on paper towels.