Preheat the oven to 400 degrees F. Peel and cut the eggplant into 1/4-inch slices and set aside.
Combine the soy milk and egg replacer and a pinch of salt (if desired) and mix well. Set up a breading station with one bowl for each: flour, egg replacer mixture, and bread crumbs. Dredge the eggplant in flour and shake off the excess. Submerge the eggplant in the egg replacer mixture, shake off the excess, then coat evenly with bread crumbs. Place the eggplant in a single layer on a lightly greased baking sheet. Bake, uncovered, for 15 to 20 minutes, or until the eggplant is crisp on the outside and tender inside.
Place the eggplant slices on the sub rolls, top with marinara sauce, and serve immediately.