Confession, I use these things in everything. These roasted tomatoes are what I use for my homemade marinara and they are also great on grilled cheese sandwiches. They are so rich in flavor that you'll be surprised at how easy they are to make. And once you make them, you'll be even more surprised at where they end up.
Slice the tomatoes so they are about 1/4 inch thick. I find the meatier they are the better they turn out.
On a parchment-lined baking sheet, spread the tomatoes out in a single layer and drizzle olive oil over them. Then sprinkle them with the chopped rosemary. Add the cloves of garlic to the sheet, leaving them peeled and in tact.
Roast the tomatoes for 6 hours at 200 degrees F. The meat of the tomato should shrivel but they will still be a bit liquidy.