Heat 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 35 to 40 minutes until soft with browned edges.
Meanwhile, combine broth, rice, and tomato paste in a soup pot. Cover; gently simmer 20 to 25 minutes until rice is very soft.
Scrape vegetables and all juices into pot. Simmer 5 minutes; remove from heat.
Blend thoroughly with an immersion blender, keeping blade submerged. Press through a fine sieve into a clean saucepan; discard skins and seeds.
Add cream; warm on low 3 to 5 minutes until steaming, not boiling. Divide smooth bisque among 4 bowls.