Place the pork roast, either frozen or thawed into a crock pot, add a little water or stock to the bottom of the pot and cook on low for 8-12 hours or until very tender and falling apart.
About 4 hours before your pork roast is done quick soak the beans in a large stock pot according to the package directions (sort, rinse, cover with 12 cups water, boil rapidly for 2 minutes and let sit, covered for 1 hour).
While the beans are soaking prepare your serrano peppers. If using dried peppers, remove the stems (and seeds if desired - I leave mine in), cover with boiling water and let steep, covered for 30 minutes. Process the peppers and the rehydration liquid in a food processor or blender until finely chopped. If using fresh peppers simply dice them up, again removing the seeds if desired.
Drain and rinse the beans, return them to the pot and add the chicken stock, peppers, and enough water to just cover the beans. Simmer for about 3 hours or until tender and most of the liquid has been absorbed. Check on the beans periodically to make sure they have enough liquid - you may need to add liquid a couple of times before the beans are tender. (You can add any liquid you want - I add some liquid from the pork roast which is delicious but you could add either water or more stock as well!).
When beans are finished cooking, add the tomatoes, red wine vinegar, and all the seasonings and stir well to combine. Continue to simmer on the stove over low heat while you shred the pork.
Shred the pork roast, removing the fat and place the meat in a large bowl. Add the shredded cheeses on top of the pork and pour the finished beans over the cheese. Stir everything together - the hot pork and beans should melt the cheese!
Place the filling inside the tortialls (you can warm them first if desired - I don't but I do place the wrapped burrito into the microwave with cheese sprinkled on top and microwave it for a minute to melt the cheese and heat everything well!) and serve with hot sauce if desired!