Heat oven to 425 degrees F and halve new potatoes.
On a baking sheet, toss the potatoes and broccoli with 2 tablespoons of the oil, 1/2 teaspoon salt, and 1/4 teaspoon black pepper. Roast, tossing once, until the vegetables are tender, 25-30 minutes.
Meanwhile, in a small bowl, whisk together the miso, vinegar, 1 tablespoon of the remaining oil, and 3 tablespoons water.
Heat remaining teaspoon of oil in a nonstick skillet over med-high heat. Season the salmon with 1/4 teaspoon each salt & pepper and cook until opaque, 3-4 minutes per side.
Drizzle salmon with miso sauce, sprinkle with the crushed red pepper, and serve with vegetables.