Prepare pork roasts by boiling the meat with about 2 tablespoons of garlic salt per roast. Use as many pots as you need to accommodate the roast. Cook the meat until fork tender and comes apart with no resistance. This usually takes about 2 hours. Reserve pork broth. Pull meat apart into chunks and refrigerate until ready to use.
While the meat is cooking, clean dried chilies by removing the tops and discarding the seeds. Place pods into a bath of water and soak for a few minutes. While pods are soaking, fill a large pot halfway with water. Place your clean chili pods in the water and push them down until the water covers all. Bring to a boil and then simmer 34 to 45 minutes. When done, remove from heat.
Transfer small bunches of the tender chili pods to a blender and blend on high until the pods turn to a liquid mixture. (The seed and skins will make the mixture seem a little chunky but that will be removed in a food mill.) Pour the chili sauce into a food mill which should be attached to a bowl or saucepan. Run the sauce through the mill until no more liquid is left in the top of the mill. Discard the leftover seeds and skin. Repeat this process for the remaining chili sauce until all of it has been run through the food mill. Next, add the ground cumin to the chili sauce. This sauce uses quite a bit of salt; add small amounts at a time, to taste.
Once chili sauce is properly seasoned, add pork to the chili sauce. Stir until thoroughly mixed. No need to heat, just put the mixture in the refrigerator until ready to use.
Open packages of cornhusks and remove the silk from each husk. Place cornhusks into a sink filled with warm water. Let the husks soak for about 3 minutes. Remove the husks from the water and place on a cookie sheet and cover with damp towel to keep moist.
Prepare masa according to the directions on the package, or buy pre-made masa, available at specialty ethnic food stores. Also try calling a Mexican restaurant, they may make it for you. To soften up the masa before you work with it, add approximately 2 cups of the reserved pork broth.
Once softened, divide masa into deep bowls amongst the people helping. Press masa flat, down into the bowl, creating a flat surface. Take 1 cornhusk and lay it flat, add a large dollop of the masa onto the husk. Spread the masa out onto the leaf with the back of a spoon to create a thin paste like coverage, being sure to leave no holes. Place 2 tablespoons of the chili sauce/pork mixture onto the masa. (It?s best to keep a bowl of the sauce next to you at all times.) Fold the tamale bringing two sides together so that they slightly overlap, then fold the bottom up over the folded sides. Press down slightly on top of tamale while holding everything in place and the masa will act as a glue to seal the filling.
Place tamales standing upright into a large double steamer. Steam for 2 hours. Remove tamales from steamer and let stand about 5 minutes. Pull off husk and eat. If desired, tamales may be frozen in plastic storage bags. To steam frozen tamales, just add 1 hour to the cooking time.