This method of slow roasting tomatoes comes to me from my good friend Lisa E.. The point isn't to completely dry the tomatoes, just to concentrate the flavors. When they're done they'll have a thick, sweet, rich tomato flavor and the texture will be moist but not juicy. Because you aren't drying them, they can't be stored in oil or in jars on the pantry shelf as you might do with dried tomatoes. If you make more than you can use, you can freeze them. I recommend using a vacuum seal if you have one. Otherwise just squeeze as much air as you can out of a freezer bag and label it with the date they were frozen.
Slice tomatoes thickly (between 3/8" and 1/2" thick). They are going to shrink quite a bit. If you are going to roast romas, trim off the tough stem end and slice them in half length-wise.
Preheat the oven to 325 degrees. Line a baking sheet with aluminum foil to catch all the drippings. Then place a drying rack on top of it. This lets the oven air circulate around the tomatoes for better drying out. If you don't have one, you can still make these, just put the tomatoes directly on the foil. They won't dry out as well but you'll still get the deepened flavor. A great alternative is to use paste tomatoes which don't drip as much. Lay the sliced tomatoes out on the rack closely together. (So you can fit as many as possible on one baking sheet). Incidentally, I always do two trays at a time. I do this because I can't make small batches of things. I like to make as much as possible. Some people call this "greed", but I prefer to call it SMART.
Brush all top sides of the tomatoes with either olive oil or other cooking oil. This will help develop a rich texture. Everything roasts better with oil.
Sprinkle with salt. Then sprinkle with SUGAR. Lisa says this is VERY important. If you have used a slicing tomato then turn them all over and brush the backsides with oil and sprinkle with salt and sugar. You won't have to do both sides if you use paste tomatoes.
Put them in the oven and cook for several hours. Yes, I know, it isn't a quick recipe, but it is so easy I think you won't mind the hours they tie up your oven racks. If you do two trays of them at once, I suggest switching the trays between the top and bottom rack every hour or so so that they all bake evenly.
They're done when they are dried out a bit (but aren't crisp), are half their original size, darkened in color, and smell richly of tomato. There's no exact baking time. It should take at least 3 hours.
So what do you do with these now? You can put them on sandwiches with roasted eggplant, cheese, and pesto. You can slice them up to add to pasta. You can eat them just as they are. You can use them to top pizzas with. You can use them in a savory tart. You can add them to soup. You can use these in almost any recipe that calls for reconstituted sun dried tomatoes.