Adjust racks to top and middle positions and preheat oven to 425 degrees. Wash and dry all produce. Trim, peel, and cut carrots on a diagonal into ½-inch-thick pieces. Toss on a baking sheet with a drizzle of oil and a pinch of salt and pepper. Roast on top rack until browned and tender, 20-25 minutes.
While carrots roast, peel and mince or grate ginger. Trim and thinly slice scallions, separating whites from greens; mince whites.
Heat a drizzle of oil in a small pot over medium-high heat. Add half the ginger; cook until fragrant, 1 minute. Stir in rice, 1¼ cups water, and a pinch of salt. Bring to a boil, then cover and reduce heat to low. Cook until rice is tender, 15-18 minutes. Keep covered off heat until ready to serve.
While rice cooks, in a large bowl, combine beef, scallion whites, panko, remaining ginger, and 1 TBSP Teriyaki sauce (2 TBSP for 4 servings; you’ll use the rest in the next step). Season with salt and pepper garlic powder. Form into 1½-inch meatballs; place on a second baking sheet. Bake meatballs on middle rack until browned and cooked through, 14-16 minutes.
Meanwhile, in a small bowl, combine sour cream and sriracha to taste. Add water 1 tsp at a time until mixture reaches a drizzling consistency. Once meatballs are done, carefully transfer to a second large bowl; add 7 TBSP Teriyaki sauce and toss to coat.
Fluff rice with a fork; taste and season with salt if desired. Divide between plates and top with carrots, meatballs, and any bulgogi sauce from bowl. Drizzle with sriracha crema. Garnish with scallion greens and as many sesame seeds as you like and serve.