Preheat your oven to 400°F (200°C) and line a baking sheet with parchment paper.
Wash the Hokkaido pumpkin thoroughly; since the skin is edible, there is no need to peel it.
Remove the seeds and cut the pumpkin into 1-inch cubes, then place them in a large mixing bowl.
Toss the pumpkin cubes with 0.5 tablespoon of olive oil, dried rosemary, dried thyme, and half of the salt and pepper.
Spread the pumpkin in a single layer on the baking sheet and roast for 25 to 30 minutes until tender and slightly caramelized.
While the pumpkin is roasting, season the chicken breast with the remaining salt and pepper.
Heat the remaining 0.5 tablespoon of olive oil in a skillet over medium-high heat.
Sear the chicken breast for 6 to 7 minutes per side until the internal temperature reaches 165°F.
Add the minced garlic to the skillet during the last minute of cooking to infuse the chicken with flavor.
Slice the chicken and serve it alongside the herb-roasted pumpkin cubes.