Preheat oven to 210ºC. Line a large baking tray with baking paper.
Add potatoes, 1 1/2 tbsp oil, oregano, paprika, 1/2 tsp garlic, 1/2 tsp rosemary, 1/2 tsp salt and 1/2 tsp pepper in a large bowl and mix well. Spread coated potatoes onto tray and bake for 30 minutes. Add onion to the bowl, toss to coat and set aside.
Combine all remaining ingredients in a second bowl and toss to coat chicken.
Place chicken fillets on baking tray with potatoes and scatter chicken with onions.
Reduce temperature to 180°C, return tray to oven and cook for a further 20-25 minutes until chicken is tender and potatoes golden brown.
Serve roasted chicken and potatoes with steamed greens and salad.