Heat the oven to 425°F. Toss tomatoes, onion and garlic with oil, salt and pepper on a large rimmed sheet, keeping tomatoes cut-side up. Roast for 35 to 40 minutes until soft and browned at the edges.
Meanwhile, combine broth, rice and tomato paste in a soup pot. Cover and simmer gently for 20 to 25 minutes until the rice is very soft.
Scrape the roasted vegetables and all their juices into the pot. Simmer together for 5 minutes, then remove from the heat.
Blend thoroughly with an immersion blender, keeping the blade submerged. Press through a fine sieve into a clean saucepan and discard the remaining skins and seeds.
Stir in cream and warm over low heat for 3 to 5 minutes until steaming without boiling. Divide the smooth bisque among 4 bowls.