Whisk together the olive oil, garlic, cumin, cayenne pepper, Italian seasoning, orange juice, and orange zest in a medium bowl. Season with salt and black pepper, to taste, and set aside.
Place the chicken thighs in a gallon-size freezer bag and pour half of the marinade on top. Seal bag tightly while removing any excess air. Turn bag several times to ensure the chicken is evenly coated and marinate at room temperature for 30 minutes or place in the refrigerator for one hour to overnight. Turn bag occasionally while marinating to evenly distribute flavors. Reserve unused portion of marinade for later use.
To prepare, place top oven rack in center position and preheat oven to 400°F. Line a large, rimmed baking sheet with parchment paper or a silicone baking mat and set aside.
Remove chicken from marinade and place on prepared baking sheet and generously season with additional salt and black pepper, if desired. Discard bag and the remaining marinade inside.
Toss the potatoes in a large bowl with the reserved, unused marinade and season with salt and black pepper, to taste. Arrange the seasoned potatoes around the chicken thighs in a single layer without overcrowding.