Combine potatoes, onion, garlic and oil in bowl with 3/4 tsp salt, 1/2 tsp dried rosemary and 1/2 tsp pepper. Toss to mix well and coat evenly.
Spread the vegetable mixture on the sheet pan.
Combine the spice mix for chicken, and then sprinkle on the skin side up of each piece. Arrange the chicken on top of the vegetables.
Bake at 350 for 40 minutes. Remove chicken and spread the fresh spinach on top of the vegetables. Return to the oven for 10 minutes until spinach is wilted.