Preheat oven to 400°F. Place large pot of water over high heat and cover. Roll up pancetta and slice into strips with sharp knife. In large pan over medium heat, cook pancetta strips until just starting to crisp, about 3 to 4 minutes. Drizzle 1 tablespoon balsamic vinegar over pancetta and stir. Allow cooked pancetta to drain on paper towel and set aside.
In medium saucepan over medium heat, melt butter. When butter has melted, whisk in flour. Continue to cook, whisking mixture, for about 30 seconds. Add rosemary and continue to cook for another 30 seconds. Slowly add warmed milk and half and half and bring sauce to simmer, stirring constantly.
Meanwhile, liberally salt pot of boiling water. Add pasta to water and cook for 1 minute less than package directions.
When sauce has come to simmer and thickened, reduce heat to low, stir in gouda and fontina until melted and sauce is smooth. Remove from heat and stir in remaining 1 tablespoon balsamic vinegar, or more if you want more pronounced flavor. Season with salt and pepper to taste. Drain cooked pasta and stir into cheese sauce until combined.
Pour pasta mixture into baking dish, and sprinkle with half of smoked gouda. Top with the cooked pancetta and then remaining smoked gouda.
Bake 15 to 20 minutes, or until topping is crisp and the cheese is bubbly. If pancetta starts to get too dark, cover with piece of aluminum foil. Serve hot.