Cook pasta in a Dutch oven according to package directions, omitting salt and fat.
Drain; set aside, and keep warm.
Cook prosciutto in a large nonstick skillet over medium-high heat 4 minutes, stirring constantly. Reduce heat to medium, add onion; cook, stirring constantly, 5 minutes or until golden. Increase heat to high, and add tomatoes; cook, stirring constantly, 4 minutes. Stir in rosemary, salt, and pepper; remove from heat, and transfer to a large serving bowl.