Grind all the ingredients for the paste to a fine paste. Add a little water to help grind well.
Scrub the potatoes and carrots well. Cut the potatoes in half. Roughly chop the carrot ( at an angle so it looks prettier). Chop the onions to fairly big pieces (maybe about 12 from half an onion).
In an oven safe casserole dish, add the chicken pieces and the vegetables. Add the olive oil, salt and the ground paste. Mix well. Rub the chicken well with the ground masala.
Arrange in such a way that chicken is resting in between the vegetables but not covered on top with the vegetables.
Roast in the oven for about 40 mins. Check for doneness. Use a meat thermometer. It should read at least 165F when you check inside the chicken. Check in various spots so you get an accurate reading.
Take out of the oven once done. Squeeze the lemon over it just before serving and garnish with cilantro.