Preheat oven to 450º.
Place tomatoes, onion, and garlic on a rimmed baking sheet. Drizzle with olive oil and salt, then toss to coat. Spread evenly on the baking sheet.
Roast for 35-40 minutes, until onions are translucent and tomatoes are slightly caramelized.
Remove from oven and let cool slightly.
Carefully purée mixture with a blender or food processor.
Place tomato mixture into a 4-quart saucepan and stir to combine with the vegetable broth, vinegar, basil, paprika, and pepper. Warm through over medium heat, about 5 minutes.