Sheet Pan Dinner with Sausage and Roasted Vegetables

1 head cauliflower, broken into florets

1 head broccoli, broken into florets

2 medium potatoes, peeled and cubed

2 large bell peppers (any color), chopped

½ cup baby carrots, or to taste

½ large onion, chopped

1 teaspoon garlic powder, or to taste

1 teaspoon dried parsley, or to taste

1 teaspoon dried cilantro, or to taste

1 teaspoon dried Italian seasoning to taste

salt and freshly ground black pepper to taste

2 tablespoons olive oil, or as needed

1 (12 ounce) package apple chicken sausage (such as Aidells®), thinly sliced and quartered

1 (12 ounce) package Italian sausage (such as Aidells(R)), thinly sliced and quartered