Preheat your oven to 400°F. Scrub the beets, wrap them individually in foil, and roast for 45-60 minutes until tender when pierced with a fork.
While the beets roast, season the chicken breast with sea salt, black pepper, and fresh thyme.
Heat a grill pan or cast-iron skillet over medium-high heat and cook the chicken for 6-7 minutes per side until the internal temperature reaches 165°F. Let it rest for 5 minutes before slicing.
Once the beets are cool enough to handle, rub the skins off with a paper towel and dice them into 1-inch cubes.
In a small dry skillet, lightly toast the walnuts over medium heat for 3-4 minutes until fragrant and golden.
In a small bowl, whisk together the olive oil and balsamic vinegar to create a simple vinaigrette.
Place the arugula in a large bowl and toss with half of the dressing. Top with the sliced chicken, roasted beets, crumbled goat cheese, and toasted walnuts.
Drizzle the remaining dressing over the top and serve immediately.