Dry the chicken with paper towels before beginning.
Salt and pepper the body cavity and place the lemon, garlic and about 2/3 of the thyme into the chicken.
Spread butter all over the surface of the skin. Salt and pepper well.
Prepare the vegetables by cutting the carrots and potatoes into bite-size chunks. Roughly cut the onions into large pieces. Place all the vegetables in the bottom of a roasting pan.
Add the chicken broth and scatter the remaining thyme over. Place the chicken on top of the vegetables in the pan.
Cook for 1 to 1 1/2 hours or until internal temperature reaches 165 degrees.
Remove the chicken from the pan and cover with foil. Allow the chicken to rest at least 10 minutes before slicing.
If desired, return the vegetables to the oven for an additional 10-15 minutes while the chicken rests.