Preheat the oven to 400ºF/200°C/Gas 6. Place a large cast-iron skillet inside to warm up while the oven preheats.
Carefully remove the hot skillet from the oven and add the olive oil and gently swirl the oil around the bottom of the pan until coated.
Arrange the sausages, red onion, garlic cloves, and tomatoes in the skillet. Season with Italian seasoning and a generous amount of salt and black pepper, to taste.
Place the skillet into the center of the preheated oven and roast for 20-25 minutes.
Remove the skillet from the oven. Add the white beans and red wine vinegar to the skillet and gently stir to combine. Be sure to flip the sausage so that they brown evenly.
Return the skillet to the oven and cook for another 10-15 minutes or until the sausages are nicely browned.
Remove the skillet from the oven and remove the whole garlic cloves. Squeeze the roasted garlic into the skillet and top with the fresh basil. Stir to combine and serve immediately. Enjoy!