Hello Carlos. Yes it is entirely possible to achieve a crispy texture without adding oil by utilizing dry heat and proper moisture management.
Here are the key principles for oil free roasting:
1. Surface moisture removal: Always pat your vegetables thoroughly dry with a clean towel before cooking.
2. High temperature: Set your oven to at least 425 degrees Fahrenheit to quickly evaporate any residual water.
3. Air circulation: Use a wire rack inside your baking sheet so hot air can circulate underneath.
For more details on healthy cooking techniques you can visit healthy eating guides.