That might be difficult, you would need a heated roller that you can accurately control the temp. You could just get an extra pot to act as a cereal cooker. Flaked oats/corn is primarily just pregelatinized , so brewers without a cereal cooker can use these adjuncts. So, If you just use a cereal cooker to gelatinize the adjunct when you need it, and store the raw material as it its you would not need to flake them.