I agree that meeting with a dietician would be a good place to start, to ensure you don't become deficient in anything critical. Finding a safe multivitamin may be helpful, too.
Rice and legumes (beans, lentils) with some steamed vegetables are a staple in our house, and look like they may meet your needs. Also, Tinkyada rice pasta might be a nice option, or Lotus Foods brand rice ramen noodles. What about milk, eggs, fish, poultry, or red meat? You could make sushi, roasted mushrooms, salads, sweet potatoes (sweet potatoes aren't related to potato and I'm okay with them, but your experience may vary), omelettes, rice pudding, etc. It takes a while to process a list of what you CAN have and come up with meal ideas that actually fit within those parameters, but it can be done. Having a list of safe ingredients and some other people to help think of new recipes can be helpful.