Remove the florets from the head of romanesco, just like you would broccoli or cauliflower.
Toss in 2 tablespoon olive oil, then add salt, pepper, and ½ the lemon juice.
Roast on parchment-lined or greased baking dish or baking sheet on 425 for approximately 45 minutes, flipping every 15 minutes, and toss in the walnuts for the last 15 minutes.
Top with the remaining lemon juice and optional grated parmesan cheese and serve!
Notes
You can substitute cauliflower and keep everything the same, or broccoli and cut the cooking time down to 15-20 minutes.