Step 1Bring large pot salted water to boil.
Step 2Place tomatoes, cut side down, in single layer in non-aluminum baking dish. Bake at 400 degrees in lower area of oven 10 minutes. Remove from oven. When tomatoes are just cool enough to handle, pinch off skins and discard. Pour juices into small dish; reserve. Cut tomatoes in coarse chunks and return to baking dish. Toss with oil, onion, garlic, rosemary, 1/4 teaspoon salt and pepper to taste. Bake 5 minutes more.
Step 3Cook pennette as directed on package until al dente. Reserve 1/2 cup cooking liquid.
Step 4To serve, toss drained hot pasta with tomato mixture. Add reserved tomato juices (strain if desired). If mixture is dry, also reserved cooking liquid as needed. Taste and adjust seasoning. Serve hot or warm. Pass grated cheese separately.