Here is a recipe that I used for shredded beef. I don't see why you cannot substitute a top round roast. You may have to reduce the cooking time since your cut is a little smaller.
Spicy Shredded Beef Burritos
Yield: 10-12 servings
4-1/2 pound bone-in chuck roast
7 ounce can diced green chiles
3 tablespoons chili powder
1 teaspoon oregano
4 cloves garlic, minced
8 ounce can tomatoes
Salt and cayenne pepper to taste
Place chuck roast on a sheet of aluminum foil, approximately 12 inches x 25 inches. Mix together green chilies, chili powder, oregano and minced garlic.
Spread this mixture on the roast and seal the foil all around.
Place in a roaster and bake at 300 degrees F. for 4 to 4-1/2 hours. The roast should be very tender and fall apart. Discard the bone and fat.
Transfer the drippings to a large pan and stir in the canned tomatoes and shredded beef.
Mix well and heat through. Add salt and cayenne pepper to taste.
Serve on flour tortillas topped with your choice of condiments, including tomatoes, cheese, lettuce, sour cream, guacamole, etc.