Preheat the oven to 425°F.
To make the herb butter, add the herbs and seasonings to the softened butter and mix well.
Remove the chicken giblets and rinse the chicken well, inside and out. Place the chicken in the roasting pan and pat it dry.
With a dessert spoon, loosen the skin and start spreading half the herb butter under the skin on the chicken breasts and drumsticks. Then, hold the chicken upright and put herb butter on the rest of the chicken. Finally, use all the herb butter to brush it evenly all over the chicken skin. This will ensure a lovely golden color.
Cut the lemon into half and squeeze the juice all over the chicken. Place the squeezed lemon wedges in the inner cavity, along with the rosemary sprigs. If you don't have rosemary, you can use thyme sprigs instead.
Tie the chicken legs with a piece of string and tuck the wing tips under the chicken to prevent it from burning.
Place the quartered onion and halved garlic on the roasting pan and place the chicken firmly on them, breast side up.
You can now add the dry white wine or low-sodium chicken broth to the bottom of the pan.
Roast the chicken for 1 hour 30 minutes or until the chicken juices between the leg and thigh run clear. You can baste the chicken twice, once at 30 minutes and then, after an hour, by spooning the pan liquid over the skin.
You can use the meat thermometer to make sure the chicken is completely cooked. It should have an internal temperature of 165 degrees where the leg meets the body of the chicken.
Remove the chicken and place it on a serving platter. Let it rest for 20 minutes before serving it.
For the gravy, collect the pan liquid. You should have two cups of liquid. If it is less than that, use the low-sodium chicken broth. Discard the onions and keep the garlic. You can remove the garlic flesh for the gravy.
Melt butter over medium heat. Now, add flour and stir continuously. Add half the liquid while whisking. The gravy should be silky smooth and without any lumps. Once the gravy thickens, season it with salt and pepper.
The roast chicken with gravy is ready!