In a large bowl, toss stuffing with water.
In a large skillet, melt butter over medium heat. Add onion, spinach, prosciutto, garlic, sage and rosemary. SautÃ© until tender, about 5 minutes.
Add spinach mixture to stuffing. Stir in heavy cream and lemon juice. Mix well.
Spoon stuffing loosely into chicken cavity, filling about 3/4 full. Fold skin over openings and close with metal skewers. Tuck wings under chicken. Place on roasting rack. Roast chicken in a 350° oven until 180° and chicken is golden, about 1 hour 30 minutes.
NOTE: Any stuffing leftover, can be placed in a casserole dish, covered, and baked beside the chicken for the last hour of cooking. Add some pats of butter to the top to keep it moist.