Combine the San-J Sweet Tamari Splash, ¼ cup olive oil, and mustard and whisk until smooth. Put the chicken thighs into a food storage bag, add the marinade and let sit at room temperature while the oven preheats.
Line a sheet pan with parchment paper. Preheat the oven to 400 degrees.
Place the vegetables on the sheet pan, drizzle with remaining olive oil and season with salt and pepper. Remove the chicken from the marinade; discard marinade. Place the chicken on the sheet pan and bake for 25-30 minutes or until the vegetables start to brown and the chicken reaches an internal temperature of 165 degrees. Drizzle the vegetables with some more San-J Sweet Tamari Splash, sprinkle with minced herbs, and serve.