Rossi is a fairly recent top-10 pick that has become a legit top-6 center at age 23. Saying no to Rust for him would be one of the dumbest things you could possibly say. It's an immediate yes before Minnesota has the chance to fire Guerin for doing it.
Rossi for Rust would be one of the worst deals made in the last decade if Minnesota actually did it.
I don't think Minnesota would do Rust for Rossi. I think they'd be interested in Rust, but Rossi wouldn't be available. The Wild likely need to add at center, as the Eriksson Ek injury has made clear, not lose one of their best ones.
That said, I'm not sure what Rust's value is. I think it's absolutely higher than what some on this board believe it is. Barring injury, he'll have his sixth straight season with 20+ goals. He already has 12. He had 28 in just 62 games last year. He's shown an ability to play with high-end players, and anyone acquiring him would want him in that role. The Wild, for example, would play him on the opposite wing of either Kaprizov or Boldy, with a healthy Zuccarello as the fourth winger in the top six.
I think Rust for Rossi is the right kind of deal the Pens should look for, but I don't think the deal with the Wild is actually realistic. What will make it tricky is there will be some teams who value Rust so highly that you'll be able to get them to add to the Rossi-type return. And there are other teams who won't value him as highly and you'd potentially need to add to get a Rossi-type return.