Preheat oven to 425F.
Drizzle garlic with some EVOO and season with salt and pepper. Wrap tightly in a foil pouch and roast 35-45 minutes or until light golden and tender.
Prick the skins of the potatoes several times with a fork and roast to tender alongside garlic, 50-60 minutes.
Arrange the tomatoes on a large baking sheet and drizzle with EVOO. Season with thyme, salt and pepper, and roast in the center of your oven until skins burst and theyre charred at the edges, 35-40 minutes.
Squish all the roasted garlic cloves into a large bowl and add the cooked potato flesh. Drain in the juice from tomatoes and mash to combine then add tomatoes and mash with potato masher. Add mixture back to the pot with the stock to thin soup a bit. Serve in shallow bowls with lots of cheese.