Preheat oven to 400 degrees F.
Cut the tofu into cubes. Place in a single layer on one side of a nonstick baking sheet. Slice an onion and place on the other side.
Place in the oven and set a timer for 20 minutes.
Then cut the eggplant into 1-inch cubes and slice the bell pepper. Place side by side on another nonstick baking sheet and place in the oven with the tofu and onion. Bake for the eggplant and bell pepper for 15 minutes.
Meanwhile, measure the garlic, ginger, lemongrass paste, and lime juice, and curry paste in a small bowl.
When there are about 8 minutes left for the vegetables in the oven, add vegetable oil to a large nonstick skillet and heat over medium heat. Add the garlic, ginger, lemongrass, lime juice, and green curry paste. Cook for 2 minutes.
Mix the coconut milk with cornstarch and add it to the skillet. Heat through and bring to a boil, stirring frequently.
When the roasted veggies and tofu are done, add them to the coconut milk mixture in the skillet and gently mix together. Serve with rice.