This is a great way to reduce the volume of your massive tomato harvest for storage! I buy lots of incredible heirloom tomatoes from Wild Boar Farms* each summer, and roast them to remove water (heirloom tomatoes are VERY wet) and concentrate their flavor. Then they go into the chest freezer for off-season use in other dishes.
*Like the look of the tomatoes you see in these pictures? You can buy seeds online at the Wild Boar Farms website. If you grow tomatoes, I can't recommend their stock highly enough.
Step 1: Prepare Tomatoes
Chop small tomatoes in half, and slice larger tomatoes in thirds or quarters. Lightly coat your baking dish in oil; I use spray canola for this part because I'm lazy and these heirloom tomatoes carry so much liquid they don't need more oil on the bottom.
Place your tomatoes in a single layer in the baking dish, then drizzle with extra virgin olive oil. Sprinkle with salt, pepper, and spices; here I used chopped fresh rosemary and dried oregano. Optional: stick garlic cloves in any remaining spaces to roast and do some serious flavor-trading.
Important storage notes: refrigeration kills off proper tomato flavor. Keep them on your counter, and check daily for softness or incipient mold. Don't wash them until you're ready to use them.
Step 2: Roast Tomatoes
Depending on the thickness of your slices and the amount of water in the tomatoes, time will vary. You can follow the smell; there will be a gorgeous roasty aroma as the tomatoes cook. I usually cook my (very watery heirloom) tomatoes for 2-3 hours.
When the tomatoes (and garlic) look like they've started to brown or dry out on the top and the liquid in the pan has begun to thicken slightly, turn the oven off and leave the tomatoes to slowly equilibrate. If you're worried about overcooking them you can remove the pan and let it cool on the counter, but the slower cooling process makes for extra-tasty flavor.
Step 3: Store for Later Use
Use them for proper Southern tomato pie, frittatas, BLTs, beans, stews, or anything else calling for tomatoes; eat them straight; drizzle them with a balsamic reduction; serve on toast with chevre. They even freeze well. Roasted tomatoes are basically concentrated tomatoey goodness, and can be used anywhere tomatoes are usually found.
I'll fill in more of these links as I document more of the roasted tomato uses we favor.