This may seem like a no-brainer but I gotta ask, validation Rule question: I want to write a validation rule that states before an opportunity can go to Closed Won, there must be two specific contract roles defined on the opportunity. Can I write a formula that references a related list on an object? Because I'm trying to insert the field but I notice that Contact Roles is not available as a field.

I assume that this is because the reference is to a related list. And if so, any idea of a better solution? I thought about creating lookup fields for both of these on the object itself, but it seems redundant.