Preheat oven to 375˚F (190˚C). Arrange tomatoes cut side up in 8 inch (2 L) square glass baking dish. Scatter garlic throughout. Drizzle oil over top. Sprinkle with pinch each salt and pepper. Roast 15 minutes or until tomatoes are soft but not falling apart. Let cool.
Meanwhile, stir together ricotta, Parmigiano, and 1/4 tsp (1 mL) pepper in bowl. Set aside.
Heat large frying pan over medium heat. One at a time, cook flatbreads 2 to 3 minutes without turning or until browned underneath. Transfer to cutting board.
Spread scant 1/4 cup (50 mL) ricotta mixture over half of non-browned side of one flatbread. Top with one-fifth of the tomatoes, basil, prosciutto and arugula. Fold over and cut in half. Repeat with remaining flatbreads and fillings.