It might be helpful to think about what you're trying to say. For example:
* "I ate rice yesterday." This is the correct way to use the word "rice" in a sentence about the past.
* "I have riced the potatoes." This is an example of using a verb, "to rice," which means to grate or mash potatoes into a rice-like texture. The past tense would be "riced."
Let me know if you can provide more context!