Take a look at serde_json::from_value and serde_json::to_value - these functions would exactly mirror that.

RON has the unique opportunity to be an "impartial" serialization format for storing structured data internally in rust programs, so that it can still be converted to other formats without having to know the original type, but to do that, you need a way to go from arbitrary rust types to a RON value, and vice versa.