Arrange two oven racks in the upper and lower thirds of the oven, then preheat to 450°F. Wash and dry the fresh produce. Medium dice the sweet potatoes. Cut the white bottoms of the scallions into 1-inch pieces, then thinly slice the hollow green tops. Pull off and discard the tough string that runs the length of each snap pea pod. Place in a bowl. Drizzle with olive oil and season with salt and pepper. Stir to coat. In a separate bowl, whisk together the curry paste and mayonnaise; season with salt and pepper. To make the dressing, halve the lemon crosswise; squeeze the juice into a large bowl, straining out the seeds. Add the ponzu sauce and sugar; whisk until the sugar has dissolved. 

Transfer the diced sweet potatoes and prepared white bottoms of the scallions to a sheet pan. Drizzle with olive oil and season with salt and pepper; toss to coat. Arrange in an even layer. Place on the lower oven rack and roast 20 minutes. Leaving the oven on, remove from the oven. Carefully add the seasoned peas in an even layer. Return to the oven and roast 2 to 3 minutes, or until the sweet potatoes are tender when pierced with a fork and the peas are bright green and slightly softened. Remove from the oven.

Meanwhile, place the fish on a separate sheet pan, skin side down. Evenly top with the curry mayo, then the breadcrumbs (pressing gently to adhere). Drizzle with olive oil and season with salt and pepper. Place on the upper oven rack and roast, rotating the sheet pan halfway through, 10 to 15 minutes, or until browned and cooked through.* Remove from the oven.

*An instant-read thermometer should register 145°F.

Add the roasted vegetables to the bowl of dressing; toss to coat. Taste, then season with salt and pepper if desired. Serve the roasted fish with the dressed vegetables. Garnish the fish with the sliced green tops of the scallions. Enjoy!