Nestle the chicken thighs on the sheet pan and season them with kosher salt and pepper. Brush the chicken liberally with the mustard glaze and drizzle a little glaze over the vegetables as well.
Scatter the thyme sprigs over the vegetables and the chicken. Roast for 30-35 mins, rotating the pan occasionally to be sure the vegetables roast evenly.
Remove when the chicken is cooked through (an instant read thermometer should read 160 degrees F) and the skin is browned and crispy. Serve immediately.