Preheat oven to 425°F.
Rinse chicken and pat dry.
Season cavity with salt and pepper.
Stuff cavity with lemon, garlic, and thyme.
Brush chicken with melted butter and oil.
Season skin with salt and pepper.
Tie legs with twine for even roasting.
Place onions, carrots, and fennel in pan.
Set chicken on top of vegetables.
Roast for 90 minutes, basting occasionally.
Check internal temperature, should read 165°F.
Remove and rest for 15 minutes before serving.