In a large resealable food storage bag, whisk together the balsamic vinegar, minced garlic, cranberry sauce, brown sugar, red pepper flakes, salt, and olive oil. This will serve as a flavorful marinade.

Using a sharp knife, pierce the ribeye roast all over to help the marinade penetrate. Place the roast into the prepared bag, seal it tightly, and massage to coat the beef thoroughly. Refrigerate overnight, turning the bag a few times to ensure even marination.

When ready to cook, preheat your oven to 350°F. Remove the beef from the marinade and gently pat it dry with paper towels to prevent excess moisture during searing.

In a large cast iron skillet, heat the vegetable oil over medium heat. Once hot, carefully add the roast and sear on all sides until a rich, golden crust forms.

Pour the reserved marinade into the pan, then stir in the beef broth. Scatter the fresh cranberries and thyme sprigs around the roast. Transfer the entire skillet to the oven.

Roast for approximately 20 minutes per pound, or until a meat thermometer inserted into the thickest part reads 140°F for medium-rare. Adjust cook time to suit your preferred doneness.

Once done, remove the roast from the oven and let it rest for 15 minutes, loosely tented with foil. Slice and serve the beef with the tangy, aromatic cranberry-balsamic pan sauce spooned over top.