Place chicken and marinade ingredients in a zip bag or airtight container and marinade for 20 minutes up to 4 hours.
Place one oven rack on the middle shelf and another directly below it. Preheat the oven to 375F. Line two baking sheets with parchment paper.
Place the chicken breasts on a baking sheet.
In the other baking sheet, place the beets, Brussels sprouts, and butternut squash. Drizzle the veggies with olive oil and season with salt, pepper, and garlic powder. Toss the veggies to combine, keeping them in separate rows (if you combine all of them the beets will change the color of the other veggies).
Place the chicken on the top rack of the oven and the veggies directly beneath. Bake for 35-40 minutes, until the chicken is cooked to 165F and the veggies are tender (depending on the size of your cubed veggies, they might need to come out sooner).
To serve, create a bed of lettuce in a bowl, top with sliced chicken, and alternating rows of roasted veggies. Drizzle with dressing.
Notes
how to prep ahead: Roast the vegetables and chicken according to recipe instructions and allow them to cool down before refrigerating in airtight containers. Prepare the homemade vinaigrette and refrigerate for up to 1 week. Reheat the chicken and veggies before serving over a bed of greens with a drizzle of dressing.