Preheat your oven to 425°F and arrange the rack to the top position. Grease a large baking sheet with olive oil or line it with parchment paper.
Place the sweet potatoes and brussels sprouts on one half of the baking sheet. Drizzle with 1 tablespoon of sesame oil, sprinkle with salt to taste, then toss to coat evenly. Roast in the preheated oven for about 15 minutes.
In a large bowl, add panko breadcrumbs and pour milk over them. Allow this mixture to sit for about five minutes. Meanwhile, chop your scallions and mince your garlic.
To your breadcrumb mixture, add ground beef along with scallion whites, grated ginger, minced garlic, salt, and gochujang. Mix until just combined and form meatballs about 1½ inches in size.
After removing your veggies from the oven, place your formed meatballs on the other side of the baking sheet. Drizzle with remaining sesame oil and bake for an additional 14–16 minutes until they reach an internal temperature of at least 165°F.
In a medium saucepan over medium-high heat, combine soy sauce, maple syrup, rice vinegar, minced garlic, grated ginger, and gochujang. Bring to a boil.
In a small bowl, mix cornstarch with water until dissolved then whisk into your boiling sauce. Continue stirring until thickened nicely.
Carefully remove baked meatballs from their pan and transfer them into your saucepan filled with BBQ sauce; toss gently until coated well. Return them back onto their baking sheet and turn your oven setting to broil.
Broil everything together for about two to three minutes until bubbly and slightly crispy on top. Serve immediately drizzled with remaining BBQ sauce and sprinkle sesame seeds and green onion tops over each serving.