1. Cook roast in roasting pan (or slow cooker), pouring onion soup mix, dissolved in 1 cup water, over it.
2. Cook at 325F for 34-38 minutes per pound.
3. Let cool thoroughly overnight in fridge.
4. Finely chop (or shred) roast beef and mix with cheddar cheese, garlic and onion powder, salt and pepper, picante sauce and onion in a large bowl.
5. Portion 1/4 cup mixture onto each corn tortilla in the lower 1/3 of the tortilla.
6. Roll up tortilla.
7. To soften tortillas, microwave between two damp paper towels for a few seconds.
8. To freeze for later, simply put seam side down on cookie sheets and freeze.
9. Flash freeze on wax papered covered cookie sheets.
10. When firm, transfer to ziplock freezer bags.
11. To Re-heat: Thaw, then lightly fry in hot oil until brown and crispy.
12. To eat them now, continue with directions for frying below.
13. Heat electric skillet to 300°F covering bottom with oil.
14. Fry taquitos with open edge down to seal.
15. Turn over fry other side.
16. Serve hot with condiments.

Someone's review of the recipe:
This is a great recipe! Although I did use a pork roast, since a beef one was the price of an arm, a leg and my first born. I did add about 1 T fresh cilantro to the mixture as well as about 1/2 cup green salsa. I also ran my tortilla through hot oil to soften them up, I didn't have any problems with the tortillas breaking apart. I went ahead and fried them up before I froze them, since I wanted my son to be able to microwave them when he needed a snack. I wasn't sure how well they would microwave, but I was surprized that they did not turn out soggy. I microwaved them on high for 1 minute 30 seconds wrapped in a paper towel. I also warmed another batch up in the oven. Turn out great also, not as crispy as freshly fried, but still pretty crisp. Heated 350 for about 10 minutes. I will never buy the ones from the grocery store again, I have now officially been spoiled. Thanks for the great recipe!!