Preheat oven to 450°F; line a sheet pan with parchment.
Whisk soy sauce, honey, vinegar, sesame oil, garlic, ginger, and cornstarch in a medium bowl until smooth.
Toss steak with half the sauce; stand while preparing vegetables.
Toss broccoli and peppers with vegetable oil, salt, and pepper in another bowl.
Spread vegetables on pan; roast 8 minutes until slightly charred.
Remove pan; push vegetables aside and arrange beef in a single layer in center.
Roast 6-8 minutes until beef is cooked through with caramelized edges. Drizzle with remaining sauce; garnish with sesame seeds and green onions.