Preheat oven to 450 degrees F. Combine rosemary, zest, red pepper flakes, and oil in a small bowl.
Toss sweet potatoes with half the spice mixture in a bowl.
Place chicken on a baking sheet lined with foil or parchment paper, season with salt and pepper, and rub with remaining spice mixture.
Place potatoes around chicken on sheet pan.
Place pan in oven and roast ~40-45 minutes, until potatoes and chicken are golden brown and cooked through.
Serve with pan juices and sprinkled with parsley.