Castellanos is under contract for four more years at $20 million per. He's 30. I don't think he'd bring much in the way of prospects; if that contract is tradable, I would expect it would be in return for taking on somebody else's big, suspect contract, not for prospects who are actually worth getting.
Nola would be very tradable, IMHO, but more likely to be traded at next season's trade deadline than this winter (if the Phils are not contending - but they will be). The Phils hold a $16 million club option for 2023; that's a very reasonable price for a pitcher who has now pitched more innings than any other NL pitcher in 2022, and put up 6.0 bWAR. I mean, $16 million for 6 WAR? I know people are unhappy with him because he's kind of hit the wall here...but 205 innings, 3.25 ERA, 6 WAR? Yeah, they could get prospects for Nola, but they have holes in the rotation as it is (Wheeler, Nola, Suarez, ??, ??). Gibson and Syndergaard are free agents; Eflin is likely going to stay in relief (I'm assuming it's a better use of his creaky knees). After that, it's Falter, Sanchez, Painter, Abel, McGarry. Three of them in the Opening Day rotation (assuming Nola is traded)?