Cook onions, bell pepper, and garlic in same skillet over medium-high heat, stirring occasionally and scraping bottom of pan, until tender and beginning to brown, 10–12 minutes. Add wine and cook, stirring occasionally, until reduced and you can no longer smell the alcohol, about 8 minutes. Add broth, peppers, vinegar, and rosemary and bring to a boil; cook until slightly reduced, about 5 minutes. Nestle chicken into onion mixture, then transfer skillet to upper rack of oven and roast chicken 10 minutes. Add sausages to skillet, pushing them into onion mixture, and continue to roast until chicken is cooked through and an instant-read thermometer inserted into thickest part of thigh registers 165°, 5–10 minutes.