Adjust rack to top position (top and middle positions for 4 servings) and preheat oven to 425 degrees. Wash and dry all produce. Trim and thinly slice scallions, separating whites from greens. Peel and mince or grate ginger. Dice sweet potato into ½-inch pieces. Trim and quarter mushrooms. Core, deseed, and dice bell pepper into ½-inch pieces.

Melt 1 TBSP butter (2 TBSP for 4 servings) in a small pot over mediumhigh heat. Add scallion whites and 1 TBSP ginger (2 TBSP for 4); cook, stirring, until fragrant, 1 minute. Add rice, 1¼ cups water (2¼ cups for 4), and a pinch of salt. Bring to a boil, then cover and reduce to a low simmer. Cook until rice is tender, 15-18 minutes. Keep covered off heat until ready to serve.

Meanwhile, in a medium bowl, toss sweet potato and mushrooms with a drizzle of oil, half the hoisin (you’ll use the rest later), salt, and pepper. Spread out on one side of a baking sheet. Toss bell pepper on empty side with a drizzle of oil; season with salt and pepper. Roast on top rack until just tender, 15 minutes (they’ll finish cooking in step 5). (For 4 servings, use 2 sheets; roast sweet potatoes and mushrooms on top rack and bell peppers on middle rack.)

While veggies roast, in a small bowl, combine mayonnaise, sour cream, soy sauce, and as much sriracha as you like. TIP: Start with half the sriracha, then taste and add more from there if you like things spicy.

Once veggies have roasted 15 minutes, remove baking sheet from oven. (For 4 servings, remove sheet with sweet potatoes and mushrooms; leave bell peppers in the oven.) Using a spatula, toss sweet potato and mushrooms with remaining hoisin and half the sesame seeds (save the rest for serving). Return to oven until veggies are tender and glaze is tacky, 5-8 minutes more.

Fluff rice with a fork and season with salt; divide between bowls. Arrange sweet potato, mushrooms, and bell pepper on top in their own sections. Drizzle everything with as much sriracha soy mayo as you like. Top with scallion greens and remaining sesame seeds. Serve.