Warm Kale Antipasto Salad

2 red onions, halved and sliced

2 small Japanese eggplants, halved lengthwise and sliced

12 baby bell peppers (any color), halved

1 pint cherry tomatoes, halved

3 tablespoons extra-virgin olive oil, plus more for drizzling

Kosher salt and freshly ground pepper

1 5-ounce package baby kale or 8 cups chopped kale leaves

1 romaine lettuce heart, chopped

2 tablespoons balsamic vinegar

1 crusty whole-wheat roll, cubed

2 ounces deli-sliced soppressata or salami (about 8 slices), cut into strips

2 ounces pecorino romano cheese, shaved