Remove skin from garlic and separate cloves, cut off tops, leaving the root intact. Brush with olive oil, sprinkle with salt and pepper.
Wrap with foil and bake for 425 for 30-35 minutes.
Squeeze into a bowl and add lemon juice, mix.
Rub mixture on the roast and place roast in a roasting pan.
Arrange potatoes, carrots, and onions around the roast, bake at 350 for 1 1/2 hours.
Uncover and bake for 1 1/2 hours longer. Baste occasionally.
Let stand for 10 minutes.