Preheat oven to 425F. Toss together the red bell pepper, corn, onion, ½ tablespoon olive oil, ¼ teaspoon salt, and ⅛ teaspoon black pepper; spread on a large baking sheet. Roast until the veggies are tender and just starting to caramelize, about 20 to 30 minutes, stirring every 10 minutes.
Whisk together the remaining 2½ tablespoons olive oil, remaining ½ teaspoon salt, remaining ⅛ teaspoon black pepper, vinegar, mustards, and honey in a large bowl; set aside.
Add the potatoes to a medium saucepan and cover with cold water by about 2 inches. Bring to a boil, then turn heat down and simmer until the potatoes are fork-tender.
Drain the potatoes and immediately toss them in the dressing, then gently toss in the roasted veggies and chives (the potatoes will absorb the dressing and become incredibly flavorful if you make the salad ahead of time; if you do so, keep it in the fridge until serving).
Taste and season with additional salt and pepper as desired; serve hot, cold, or room temperature.
Recipe by An Edible Mosaicâ„¢ at https://www.anediblemosaic.com/roasted-veggie-potato-salad/