Preheat your oven to 400°F and line a large baking sheet with parchment paper for easy cleanup.
Toss the cubed butternut squash and the chicken breast with olive oil, sea salt, black pepper, dried thyme, and dried sage until evenly coated.
Spread the squash and chicken in a single layer on the baking sheet and roast for 20 to 25 minutes until the squash is tender and the chicken is cooked through.
Remove the chicken from the oven and let it rest on a cutting board while you prepare the soup base.
In a small skillet, sauté the diced yellow onion and minced garlic with a splash of the vegetable broth over medium heat until they are soft and translucent.
Transfer the roasted butternut squash, sautéed onion mixture, and the remaining vegetable broth into a high-speed blender.
Blend on high until the soup reaches a completely smooth and velvety consistency, adding a touch more broth if a thinner soup is preferred.
Slice the roasted herb chicken into thin strips or bite-sized pieces.
Pour the warm butternut squash soup into a bowl and top with the sliced chicken breast to serve.