1. Cut rolls in half horizontally. Pull out soft centers, making bread shells about 1/2 inch thick. Reserve soft bread for another use. Set rolls in a single layer on a 14- by 17-inch baking sheet.
2. Broil rolls about 4 inches from heat, turning once, until lightly toasted on both sides, about 3 minutes total.
3. Meanwhile, scoop beans into a microwave-safe bowl; cover. Heat in a microwave oven at full power (100%) until hot, about 2 minutes; stir at least once.
4. Spread refried beans equally on cut sides of each roll section. In bottom section of each roll, tuck equal portions of the filling, onion, tomato, chilies, and cabbage. Sprinkle lightly with salt and pepper.
5. Cut avocado in half lengthwise; discard pit. With a large spoon, scoop avocado from shell (or pull off peel), chopping slightly. Place equal portions of avocado on cut sides of the roll tops and spread to cover; sprinkle lightly with salt and pepper. Set tops, avocado down, on sandwich bases. Press down to secure filling. Serve with salsa to add to taste.
Egg-chorizo filling: Chop 1/3 pound cooked or smoked chorizo or linguisa sausage. In a bowl, beat 8 large eggs to blend with 2 tablespoons water and 1/4 teaspoon salt. In a 10- to 12-inch nonstick frying pan over medium-high heat, stir chorizo until lightly browned, 3 to 4 minutes. Add egg mixture. As mixture sets, use a wide spatula to push cooked eggs aside and let uncooked liquid flow to pan bottom. Cook until eggs are softly set, about 2 minutes. Add salt and pepper to taste.
Per sandwich: 737 cal., 43% (315 cal.) from fat; 37 g protein; 35 g fat (10 g sat.); 68 g carbo (3.9 g fiber); 1,804 mg sodium; 458 mg chol.
Ham and cheese filling: Use 3/4 pound thinly sliced cooked ham and 1/4 pound sliced asadero or jack cheese.
Per sandwich: 659 cal., 36% (234 cal.) from fat; 42 g protein; 26 g fat (9.1 g sat.); 66 g carbo (3.9 g fiber); 2,549 mg sodium; 75 mg chol.
Chicken filling: Use 3/4 pound purchased cooked, seasoned chicken breast strips or sliced, cooked chicken breasts.
Per sandwich: 522 cal., 22% (117 cal.) from fat; 36 g protein; 13 g fat (2.7 g sat.); 67 g carbo (3.9 g fiber); 1,537 mg sodium; 56 mg chol.
Cheese filling: Use 3/4 pound panela or fresh mozzarella cheese, cut into 1/4-inch-thick slices.
Per sandwich: 658 cal., 48% (315 cal.) from fat; 31 g protein; 35 g fat (17 g sat.); 66 g carbo (3.9 g fiber); 1,613 mg sodium; 30 mg chol.