Preheat oven to 400°F (200°C). Line a baking sheet with foil and place a wire rack on top.
Whisk soy sauce, brown sugar, honey, vinegar, sesame oil, garlic, ginger, and pepper in a bowl.
Pat drumsticks dry and toss with half the sauce. Arrange on the rack.
Roast 25 minutes, turning once. Reserve the pan juices.
Pour reserved juices into a small pan and bring to a simmer.
Stir in cornstarch slurry and cook until sauce thickens, about 1 minute.
Brush thickened sauce on drumsticks and roast 5-8 more minutes until sticky and glazed.
Garnish with sesame seeds and green onion. Let rest 5 minutes before serving.