Freezing tomatoes (or any type of fresh produce, for that matter) is more complicated than simply tossing them into the freezer. You must carefully clean and prepare them, and you've got to follow a specific series of steps if you want them to be worth eating after you thaw them out.
The first thing you need to realize about freezing tomatoes — regardless if you're freezing them whole, blanched or stewed — is that they're going to be somewhat mushy after you thaw them. There's not much you can do to prevent this. The cellular damage that occurs during the freezing process is irreversible and unavoidable. Therefore, frozen tomatoes tend to make better sauces, soups and stews than they do toppings for your hamburgers or salad components.
Roma tomatoes are a popular choice for freezing, especially when you plan to use them in future sauces, but there's no single variety of tomato that is the best (or worst) candidate for freezing. Preferences vary per person, and one seasoned tomato freezer might warn you about freezing cherry tomatoes, for example, while another might swear by them.
What most people agree upon is the state the tomato should be in before you put it into a deep freeze. The ideal tomato should be firm and blemish-free. As with virtually all foods, the fresher it is, the better, so don't stick your suspicious-looking three-week-old tomatoes in the ice box and expect them to be edible after you thaw them out. In fact, if you have a cracked, mushy, discolored or browning tomato, you should discard it, as the freezing process will only amplify its faults.