A twist on classic Sloppy Joes, these delicious (and not so sloppy) Italian-style mini-sandwiches are a fabulous game day snack. Everyone I've served them to has raved, even people who don't like traditional Sloppy Joes! Because the sauce is thick and chunky and the sandwiches are small, there is no need to worry about them creating a big mess. Enjoy!!
Heat 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.
Add 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 adjust seasonings.
Preheat broiler. Brush cut sides of roll tops lightly with oil. Arrange all roll slices, cut side up, on a large baking sheet.
Using 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.