Preheat oven to 400 degrees F. Cook the rice according to package directions (if using microwaveable rice, you can do this step just before serving).
Meanwhile, transfer the broccoli bell pepper, and onion to a large rimmed baking sheet and toss with 2 tablespoons olive oil. Season with salt and pepper, to taste. Transfer the baking sheet to the preheated oven and roast for 20 to 25 minutes, or until browned and fork tender, tossing with a spatula once or twice through the cooking time.
While the veggies are roasting, in a small bowl, whisk together the soy sauce, brown sugar, sesame oil, ginger, garlic, red pepper flakes, and cornstarch. Set aside
Heat the vegetable oil in a 12-inch skillet over MEDIUM-HIGH heat. Cook, stirring occasionally to break up the beef, leaving some chunky texture to the meat (don’t smash it until it’s finely ground). Drain off the excess grease, return the skillet to the heat, and season with ½ teaspoon salt and black pepper, to taste.
Reduce the heat to MEDIUM-LOW. Stir in the soy sauce mixture and cook, stirring occasionally for 2 to 3 minutes to allow the sauce to combine with the beef and thicken slightly. Remove from the heat and garnish with green onion and sesame seeds.
Serve the beef over cooked rice with the roasted veggies. For a deliciously spicy kick, top the bowls with Go-Chu-Jang.