To make rolled stuffed turkey breast: Preheat oven to 375 degrees F. Lightly oil a baking sheet or coat it with cooking spray.

Slice off stem ends from tomatoes, quarter them lengthwise and arrange on the prepared baking sheet, skin-side down. Drizzle with 1 tablespoon olive oil. Season with salt and pepper. Roast until the tomato skins are wrinkled and browned, 50 to 60 minutes. Set aside to cool.

Meanwhile, spread breadcrumbs on a second baking sheet and bake until well toasted, about 5 minutes. Cool briefly, then transfer to a small bowl. Stir in parsley, garlic and 1 1/2 teaspoons of the thyme; set aside.

Remove skin from turkey breast and discard. Set the breast on a cutting board, skinned-side-down. Insert a sharp knife, preferably a boning knife, between the breast muscle and the rib cage of one side of the turkey breast; carefully cut the breast meat away from the ribs. Leave the meat attached at the breast bone. Repeat on the other side. Finally, use the knife to carefully release the whole breast from the breastbone, without separating the breast halves. Trim fat and remove large white tendons from tenderloins. Place the breast, skinned-side down, on the cutting board. Fold open the tenderloin flaps so the piece is somewhat rectangular. Cover the turkey breast with plastic wrap. With a meat pounder, rolling pin or heavy pan, pound the meat to an even thickness of about 1/2 inch. Discard plastic wrap and season the turkey with salt and pepper.

Place two 14-inch sheets of plastic wrap overlapping on a work surface; set the flattened turkey breast on top with a long side toward you. Sprinkle the meat evenly with half of the reserved breadcrumb mixture, leaving a 1-inch border. Arrange prosciutto over top. Cover with the roasted tomatoes, smearing them slightly with a spatula to form an even layer. Top with the remaining crumb mixture.

To keep the stuffing from falling out during roasting, fold over the two short sides by 1 inch. Starting at the side closest to you, roll the meat as you would a jelly roll, using the plastic wrap to assist and lift in the rolling. Tie butcher's twine firmly around the length of the roll, then secure with crosswise ties at 1-inch intervals. Season all over with salt and pepper.

Heat the remaining 1 teaspoon olive oil in a large roasting pan over high heat. Brown the roll well on all sides, 5 to 7 minutes. Slip a rack under the browned roll. Sprinkle with remaining 1/2 teaspoon thyme. Tent with foil.

Bake until a meat thermometer inserted into the center registers 160 degrees F, 60 to 70 minutes. Transfer the roll to a platter and let cool. Cover and refrigerate until firm, at least 4 hours.

To make sauce: Combine sour cream, basil, parsley, garlic and lemon juice in a food processor or blender; process until the sauce is a vibrant green. Transfer to a bowl and season with salt and pepper.

To serve: Remove the string from the turkey roll and carve into 1/4-inch-thick slices. Arrange on a platter and serve with the Creamy Basil Sauce.