Preheat oven to 500 degrees
Chop garlic, rosemary, sage and thyme. I like to make a pile of the herbs including the garlic and salt & pepper and then chop them with a knife called a Mezzaluna. It takes no time at all to chop herbs with this tool. You can use a standard chef's knife as well.
Combine the herb mixture thoroughly into softened butter.
Rinse chicken under cold water and pat dry with clean towel or paper towels.
Rub butter mixture all over chicken skin (I use my hands for this)
Arrange a rack in upper third of oven
Place chicken, breast side up, in a 9X12 glass Pyrex dish or in a roasting pan.
Put chicken in oven and start on potatoes
Poke wholes with fork around each sweet potato
Wrap each potato individually. First in parchment paper, then in foil
Put on a sheet pan and into oven on a rack underneath chicken
Cook chicken for 20 mins on 500 degrees or until skin is a light golden brown color
Turn oven down to 400 degrees
Roast chicken and cook potatoes for an additional 30-35 mins or until thermometer inserted into the thickest part of the thigh registers 165°F. Let rest for 10 minutes.
While chicken is resting, you can pull sweet potatoes out of oven and either split in half and serve on plates with a pat of butter or scoop out the innards and blend with an immersion blender or hand blender and spoon onto plates
Now carve the chicken and serve