Preheat your oven to 400°F and line a baking sheet with parchment paper.
Peel the golden beets and cut them into uniform 1/2-inch cubes.
Toss the beets on the baking sheet with half of the olive oil, minced rosemary, and a pinch of salt and pepper.
Roast the beets for 25 to 30 minutes, or until they are tender and the edges are slightly caramelized.
While the beets roast, season the chicken breast with the remaining salt and pepper.
Heat the remaining olive oil in a skillet over medium-high heat and sear the chicken for 6-7 minutes per side until cooked through.
In a small bowl, whisk together the lemon juice and Dijon mustard to create a zesty dressing.
In a large bowl, combine the roasted beets, toasted walnuts, and arugula.
Drizzle the dressing over the beet mixture and toss gently to coat.
Slice the chicken breast and serve it warm over the herb-roasted beet salad.