Thaw rolls at room temperature until soft but still cold, about 10 minutes.
Spray cookie sheet with cooking spray.
Cut each roll into quarters; shape dough pieces into balls.
Place on cookie sheet.
Brush tops of dough balls with butter.
Cover with plastic wrap sprayed with cooking spray.
Let rise in warm place 2 hours to 2 hours 30 minutes until doubled in size.
Heat oven to 350°F.
Remove plastic wrap.
Bake buns 12 to 15 minutes or until golden brown.
Remove from pan to cooling rack.
Meanwhile, in medium bowl, mix salsa ingredients.
Cover; refrigerate until serving time.
In 10-inch nonstick skillet, heat 1 teaspoon of the oil over medium heat.
Add onion; cook 3 to 4 minutes, stirring often, until softened.
Remove from heat; cool slightly.
In medium bowl, mash beans with potato masher or fork, leaving a few beans whole.
Stir in egg, bread crumbs, garlic, cumin, salt and pepper.
Add cooled onion; mix until thoroughly combined.
Shape mixture into 20 (1-inch) balls, using about 1 scant tablespoon per ball.
In same skillet, heat 2 teaspoons oil over medium heat.
Place half of the bean balls in skillet; with back of spatula, flatten balls into patties, about 11⁄2 inches in diameter.
Cook 4 to 6 minutes, turning once, until browned.
Remove from skillet; cover to keep warm.
Repeat with remaining 2 teaspoons oil and bean balls.
Split buns in half.
On bottom half of each bun, place lettuce piece, bean patty, cheese quarter and 1 heaping tablespoon corn salsa.
Cover with top halves of buns.