Preheat oven to 400F.
Clean and rinse the bok choy, trim off the stems at the bottom, slice and quartered. Prepare the dressing by combining the soy sauce, sugar, apple cider vinegar, sesame oil and sesame seeds. Stir to mix well, set aside.
Toss the bok choy with the olive oil and black pepper. Arrange them on a baking sheet lined with parchment paper.
Roast in oven for 8 minutes. Transfer the bok choy to a serving platter, drizzle the sauce and serve immediately