Preheat oven to 350 degrees F (175 degrees C). Lightly grease a medium baking sheet.
Remove stems from mushrooms. Reserve and chop approximately 1/2. Arrange mushroom caps in a single layer on the prepared baking sheet so that the edges of the caps touch one another. Set aside.
In a small saucepan over medium heat, melt 1/2 cup butter. Place reserved, chopped mushroom stems in the pan, and slowly cook and stir until soft. Stir in the flour to coat mushroom stems. Mix in green onions, sherry, minced clams and 1/2 their reserved juice (discard remainder), garlic, bread crumbs, pepper, Italian-style seasoning and bacon bits. Continue cooking approximately 3 minutes, until all ingredients are well mixed. Remove from heat and stir in Romano cheese. Allow mixture to cool approximately 5 minutes.
Fill the mushroom caps generously with the mixture. Drizzle with melted butter.
Bake in the preheated oven 20 to 25 minutes, until lightly browned. Serve with lemon wedges.