Toss grapes tomatoes with olive oil, salt and pepper. Add to parchment lined baking sheet and bake for 20-25 minutes.
While tomatoes are in the oven, add olive oil to saucepan and heat over medium-low. Add onion and pinch of salt and cook 3-4 minutes. Add garlic and thyme; cook 2 minutes.
Add whole can of tomatoes with juice, 2 cups of the broth and basil. Break up the tomatoes slightly with a wooden spoon. Bring to a boil then reduce to low and simmer uncovered for 25 minutes.
Let cool slightly and add to a blender along with roasted tomatoes. Puree, add more broth if you like a thinner consistency. Transfer back to pot and season with salt, black pepper, crushed red pepper to taste.