Preheat oven to 425 degrees. Combine broccoli and cauliflower in a large bowl.
In a small bowl stir together olive oil, salt and pepper, garlic powder (or minced garlic) Italian seasoning, and lemon juice, Pour mixture over veggies and toss to coat well.
Spread veggies out on a large baking sheet making sure the veggies are in one layer and not overlapping or piled on each other. (You can add lemon slices here if you like for added lemon flavor and garnish). If using parmesan cheese, sprinkle over veggies now.
Cook in preheated oven for 15-20 minutes until veggies are fork-tender and begin to brown on the edges. Serve immediately.