Peel the brussel sprouts and cut off the ends. Chop an onion. Slice the baby bella mushrooms into thick slices and cut off the ends. Line a baking sheet with parchment paper. Put the vegetables in a single layer on the baking sheet. Drizzle olive oil and garlic over everything and stir. Sprinkle with a little sea salt and bake at 375 for 30-40 minutes.
You can add cauliflower pieces, yellow squash, cherry tomatoes, potatoes, etc. If you like….Cut them to about the same size as the brussel sprouts for even roasting.