Preheat the oven to 350 degrees F. Line a sheet tray with parchment paper.
Strain the canned tomatoes from their juice and reserve the juice. Put the canned tomatoes on the prepared sheet tray, add the carrots, celery, shallots and cherry tomatoes if using and drizzle with the olive oil. Season generously with salt and pepper and top with the thyme sprigs if using.
Roast the vegetables for 1 hour. Add the sherry wine and roast for another 5 minutes to "deglaze" the pan and allow the alcohol flavor to dissipate. Let cool slightly.
Discard the thyme stems if using, then transfer the roasted vegetables to a blender and blend until smooth. Thin out the soup with the reserved tomato juice as needed. Season with salt and pepper. Add the cream and blend until combined. If desired, add 1 to 2 tablespoons sherry vinegar to bump up the acid flavor. Serve immediately.