Potatoes, Carrots & Onions

1 Medium Potato per person, diced to 1/4" cubes
1 Carrot per person, pealed & sliced
2 Medium Onions coarsely chopped
Wrap everything in aluminum foil
Place on the grill for the last 1 to 1-1/2 hours of the cooking tirne of roast or place on grill and cover for 45 rnin. before spreading the coals for broiling