Heat the oven. Preheat to 425°F (220°C).
Line a large baking sheet with parchment for easy cleanup.
Prep the veggies. Chop peppers, onion, zucchini, and eggplant into bite-size pieces. Halve the cherry tomatoes.
Season and roast. Toss vegetables with olive oil, smoked paprika, oregano, garlic powder, salt, and pepper. Spread in a single layer.
Roast for 20–25 minutes, stirring once, until tender and caramelized. Add tomatoes in the last 10 minutes so they soften but don’t collapse completely.
Make the couscous. Bring broth (or water), olive oil, and salt to a boil. Stir in couscous, cover, and remove from heat.
Let sit for 5 minutes, then fluff with a fork to separate the grains.
Whisk the dressing. In a small bowl, whisk olive oil, lemon juice, Dijon, garlic, honey, salt, and pepper until emulsified. Taste and adjust lemon or sweetness as needed.
Combine. Add the roasted vegetables to the fluffed couscous. Pour in most of the dressing and toss gently.
Fold in herbs, nuts, and cheese if using.
Adjust and serve. Taste and add the remaining dressing, extra lemon, or salt and pepper. Serve warm, at room temperature, or chilled.