Preheat the oven to 400˚F and arrange a rack in the center of the oven.(Please see the section above in the blog post for Step-By-Step instructions with photos.)
Gather all ingredients. Wipe the mushrooms clean with a dry paper towel. Unless the mushrooms are very small, cut them down into small, bite-sized pieces of approximately the same size.
Combine the mushrooms, sausage, fennel, garlic and half the herbs in a large bowl and toss them with the oil. Then, arrange them in a single-layer on a large parchment-lined, rimmed sheet pan (or two sheet pans).
Roast uncovered for about 30-35 minutes, or until all items are tender and slightly caramelized. Rotate the sheet pan once about halfway through the cooking process.
Sprinkle the roasted vegetables with salt and black pepper, then toss them with the remaining fresh herbs until all ingredients are well-combined. Serve immediately.
