Preheat oven at 450 F. In a large bowl toss mushrooms with 2 tbsp melted butter, thyme, garlic, salt and pepper. Spread mushrooms in a single layer on a baking tray and roast for 25 minutes or until mushroom edges start crisping up. Transfer mushroom and juices into a large pan Cook tortelloni according to packaging instructions Strain tortelloni and gently toss with the sauce. Cook for 1 minute Remove pan from the stove and fold in 4 tbsp cold butter. Gently stir until butter is melted.