Heat oven to 425°F. Toss tomatoes, peppers, onion, and garlic with oil, salt, and pepper on two rimmed sheets. Roast 30 to 35 minutes until softened with browned edges.
Transfer vegetables and juices to large pot. Add beans, broth, and basil; simmer 10 minutes.
Turn off heat; immersion-blend smooth, keeping blade submerged. Add balsamic vinegar.
Divide cooked soup among 6 shallow freezer containers; refrigerate within 2 hours and chill fully. Leave 1 inch headspace, seal, label, and freeze up to 3 months.
Loosen one frozen portion into saucepan with 1 tablespoon water. Cover; warm over medium-low 15 to 20 minutes to 165°F, stirring and breaking up block as it softens.
Stir thoroughly; serve one container per portion, adding only a little water if too thick.