Heat oven to 425. Line a rimmed large metal baking sheet with parchment. Toss the cauliflower florets and bell peppers in olive oil and salt, then spread out on the baking sheet. Roast for 15 minutes, flip, then roast another 15 minutes or until tender and golden brown on the edges.
Meanwhile, heat the marinara in a small pot over medium-low heat. Stir in the olives, nutritional yeast, oregano, red pepper flakes and black pepper.
Fold the roasted vegetables into the warm sauce, then spoon into an oven-proof bowl.
Top the mixture with a squeeze of lemon juice, followed by the Parmesan/feta and panko.
Bake for 5 minutes, or until the cheese starts to melt and the vegetables are hot.
Top with thinly sliced basil before serving.
