1. Dissolve yeast and sugar in water and juice. Add flour and water and knead to form a dough. Cover and let rise for 30 minutes.
2. Preheat oven to 400 degrees Fahrenheit.
3. Toss vegetables on a large baking sheet with oil and salt. Roast for 20 minutes.
4. Grease two (nine-inch) round springform pans (or disposable nine-inch round pans) with cooking spray.
5. Divide dough into quarters, then roll each into a 10 inch circle. Press one circle of dough into the bottom and up the sides of each pan.
6. Sprinkle 3/4 cup mozzarella cheese on each pizza and top with roasted vegetables. Top with a second circle of dough and pinch the top and bottom to seal. Bake for 30 to 35 minutes, until golden.
7. Spread half of the pizza sauce onto each pizza and top with remaining mozzarella cheese, plus additional diced vegetables, if desired. Bake for another 10 minutes, until cheese is melted.