Heat a wood-fire oven over medium-high heat, about 400 degrees F.
Sprinkle the guinea fowl inside the cavity and all over the outside with salt and pepper.
In a bowl combine the oil, chopped rosemary, sage and some salt and pepper, and mix together.
Put a rosemary sprig in the birds and place both guinea fowl on a spit and place over the fire. Turn the birds on occasion, making sure the outside becomes evenly crisp from the heat of the fire. Brush the outside of the birds with the olive oil mixture using some rosemary sprigs as a brush every 5 minutes or so. Roast the birds until cooked through and the juices run clear, about 1 hour and 30 minutes.