oil in a large non-stick skillet over medium-high heat; add sausage.
Brown sausage well, breaking up links into small pieces with a wooden
spoon as they cook.
onion, vinegar, salt, black pepper and optional red pepper flakes; stir
until onion is tender. Add tomatoes and garlic; stir 30 seconds. Add
sauce; cook about 5 minutes, stirring frequently, or until liquid has
almost completely evaporated. Remove from heat; stir in basil. Taste and
Preheat broiler. Brush cut sides of roll tops lightly with oil. Arrange all roll slices, cut side up, on a large baking sheet.
an ice cream scoop, pile equal amounts of sausage mixture onto roll
bottoms; sprinkle lightly with parmesan. Top each with 1 slice of
mozzarella. Place briefly under broiler, watching carefully, until
mozzarella is melted and roll tops are toasted. Arrange roll tops over
melted mozzarella and serve.