Preheat the oven to 400 degrees F (204 degrees C). Line a large baking sheet (or two smaller ones that can fit side by side) with foil, or use a quality non-stick baking sheet.
Mix the broccoli and cauliflower florets in a large bowl. Add the olive oil, garlic, and half of the parmesan cheese. Toss to coat. Sprinkle with sea salt and black pepper, then toss again.
Arrange the veggies in a single layer on the lined baking sheet(s), giving them plenty of space. Roast for 25-30 minutes for fresh florets or 30-35 minutes for frozen ones, tossing halfway through, until the edges are browned.
Right before serving, toss the roasted broccoli and cauliflower with the remaining parmesan cheese. Sprinkle with additional salt & pepper to taste if needed.
