Preheat oven to 450 degrees. Spray a full sheet pan with nonstick oil and set aside. Combine all spices in a small bowl and whisk to form the Moroccan spice blend.
Add chicken thighs to a large bowl. Squeeze lemon juice over top of chicken then drizzle in half the olive oil and ¾ of the spice blend. Mix with a spoon or your hands to evenly coat chicken in the oil and spices.
Cut carrots into bite-sized pieces. Cut baby potatoes into halves. Cut onion into about five even pieces. Add all to a bowl followed by remaining olive oil and spice blend. Mix until veggies are evenly coated.
Place chicken thighs on prepared sheet pan with plenty of space between each. Arrange carrots, potatoes, and onion around the chicken. Bake for about 30 minutes or until chicken reaches an internal temperature of 165 degrees and juices run clean when chicken is cut.