Preparing Roasted Green Beans and Mushrooms is simple if you follow these easy steps:

1. Preheat Oven: Preheat your oven to 425°F (220°C).
2. Prepare Vegetables: Rinse the green beans and trim the ends. Slice the mushrooms if not pre-sliced.
3. Toss with Olive Oil: In a large bowl, combine the green beans, sliced mushrooms, and minced garlic. Drizzle with olive oil and toss to coat evenly.
4. Season: Add salt and black pepper to the mixture, tossing again to ensure an even distribution.
5. Arrange on Baking Sheet: Spread the vegetables in a single layer on a baking sheet. Avoid overcrowding, as this will lead to steaming instead of roasting.
6. Roast: Place the baking sheet in the preheated oven. Roast for 15-20 minutes, stirring halfway through, until the vegetables are tender and caramelized.
7. Add Vinegar or Cheese: If desired, drizzle balsamic vinegar over the vegetables during the last 2 minutes of roasting or sprinkle on grated Parmesan cheese just before serving.
8. Serve: Remove from the oven and transfer to a serving dish. Garnish with fresh parsley for added color and flavor.

These instructions will ensure you create a breathtaking and tasty side dish easily!