Whisk all the ingredients for the Kansas-Style BBQ sauce in a small bowl and set aside.
Place potatoes, carrots and Brussels sprouts into a 9-inch cast iron skillet. Place chicken thighs on top of the vegetables and using a pastry brush, generously brush Kansas-style BBQ sauce onto chicken thighs.
Cover cast iron skillet tightly with a sheet of Reynolds Wrap(R) Non-Stick Foil, with the non-stick side facing down on top of the chicken.
Place cast iron skillet onto grill and roast for 25 to 30 minutes. Remove foil and continue roasting for 15 minutes until chicken is tender and juices run clear or meat thermometer inserted into the center reads 180 degrees F.
Remove skillet from grill and let chicken cool for 20 minutes. Serve and enjoy!