You can get the spring roll wrappers at an oriental grocery store, and they will keep on your shelf indefinitely. They are fragile; keep them flat and handle them gently. Be sure they are made of rice. You CANNOT substitute egg roll wrappers in this recipe. The round ones, about 8 1/2 inches in diameter, are the easiest to work with. I like the Flying Goose brand, although the brand with a rose on the front works well, too.
Slice the tofu into 1/2 inch slices. Pat dry with paper towels. Press it for an hour or so if you have time. Put the tofu slices on a nonstick cookie pan. Add the soy sauce, trying to keep it on the tofu as much as possible. Bake at 325 for about 45 minutes, turning occasionally and adding more soy sauce if they look like they can absorb more. When they are nice and brown and dry, cut them into strips, about the size of French fries. You will need one strip per spring roll. (If you don't have time to bake the tofu, cut it into strips and fry it with the soy sauce on a nonstick skillet for a few minutes, carefully turning each strip, trying to crisp it up a little on each side.) Set aside.
Wash and dry the lettuce. Tear it into 3 or 4 inch pieces, removing stems and crisp veins. Your lettuce needs to be on the limp side. Any crisp pieces will tear the spring roll wrappers when you try to roll them.
Wash and dry the mint. Remove all stems! Set aside. (If you can't get fresh mint, you can substitute fresh cilantro, but the spring rolls will taste completely different, and my family would rather I not make them if I don't have mint.)
Shred or grate the carrots. Again, they need to be small enough pieces that they are not crisp. You may prefer your spring rolls without the carrots.
Throw the rice vermicelli into boiling water and cook until just done, about 2 or 3 minutes. Pour into a colander, and rinse with cool water. The noodles need to be well drained and cool enough to handle. Set aside.
Put an inch or two of water in a pan that is big enough to hold the spring rolls. (Cool water works fine). Separate the wrappers, and stack them in the water, making sure each one is completely covered with water before putting in the next one. Leave the wrappers in the water until they are flexible (about 2 or 3 minutes). Remove the whole stack at once, and place them on a clean wet kitchen towel, covering them with another damp towel.
Now you are ready to assemble them. Carefully remove one wrapper and put it on another surface (I use a bamboo sushi mat, but you could easily use another damp towel. If you use a plate, dump off the excess water between each spring roll.) Working quickly, put onto the wrapper 3 or 4 small pieces of lettuce, 4 leaves of mint, a handful of rice noodles, one strip of tofu, and a few tablespoons of carrots if desired. Quickly fold the bottom of the wrapper over the pile, fold in the sides, and continue to roll up. After I've done four or five, I wrap each in plastic wrap to keep them from drying out too much. If one of them is falling apart, wrap it in plastic wrap immediately. Have a piece of plastic wrap cut and ready in case one is falling apart. (If you are serving them to company, start over with a new wrapper on the ones that are falling apart.) If a lot of them are falling apart, then something may not be drained well enough, or you may be trying to fill them too full, or some of your wrappers may be defective with too many tears and holes, or too thin.
Serve cold or room temperature with sauces of your choice. NOTE: you do not EVER cook these spring rolls. When you finish rolling them up, they are done! They will keep in the refrigerator for a day or two. They travel well for lunches and outings. For an appetizer, serve one or two per person. As a main course, count on at least three per person.
SAUCES: These are good with a peanut sauce, but that wouldn't be fatfree. They are also good with a plum sauce. If anyone has a good plum sauce recipe, please send it to me. I serve them with the sweet sauce below AND a bottled chili sauce (I like Sriracha Hot Chili Sauce, made by Huy Fong Foods, Inc.)