Adjust rack to middle position and preheat oven to 425 degrees (middle and top positions for 4 servings). Wash and dry produce.

Peel and slice sweet potato into ½-inch-thick rounds. Trim and halve zucchini lengthwise; thinly slice crosswise into half-moons. Core, deseed, and dice bell pepper into ½-inch pieces. Halve, peel, and cut onion into ½-inch-thick wedges.

Toss sweet potato, zucchini, bell pepper, and onion on a baking sheet with a drizzle of oil (for 4 servings, use 2 baking sheets; roast on top and middle racks). Season generously with salt and pepper.

Roast on middle rack, tossing halfway through, until browned and tender, 25-30 minutes.

Meanwhile, pat salmon* dry with paper towels and season generously all over with salt and pepper.

Heat a drizzle of oil in a large pan over medium-high heat. Add salmon to pan, skin sides down. Cook until skin is crisp and fish is almost cooked through, 5-7 minutes. Flip and cook until opaque and cooked through, 1-2 minutes more.

Turn off heat; transfer to a plate. Reserve pan.

Heat same pan over medium-high heat. Add miso sauce concentrate, maple syrup, ¼ cup water (⅓ cup for 4 servings), and a pinch of salt. Simmer until slightly thickened, 2-3 minutes. Turn off heat. Stir in 1 TBSP butter (2 TBSP for 4) until melted.

Divide sweet potato jumble and salmon between plates. Spoon glaze over salmon; drizzle any remaining glaze over sweet potato jumble and serve.