Preheat oven to 400°F and line a baking sheet with parchment paper.
Toss zucchini, bell peppers, tomatoes, and red onion with 2 tbsp olive oil, salt, pepper, and garlic powder. Spread evenly on the baking sheet.
Roast for 20 minutes, flipping halfway through, until vegetables caramelize and soften.
Cook pasta in salted boiling water until al dente. Drain, rinse with cold water, and set aside.
Whisk together balsamic vinegar, Dijon mustard, honey, oregano, red pepper flakes, and remaining 1 tbsp olive oil in a small bowl.
Combine pasta and roasted vegetables in a large mixing bowl.
Pour dressing over the mixture and toss until everything is well coated.
Sprinkle feta on top and serve immediately or chill for later.