Roster Construction in Ottoneu: How to Build a Winning Roster

As we move deeper into the season, teams are starting to ask themselves if it is time to buy or sell and, if so, what buying or selling looks like. How aggressively do I want to ship out potential keepers for a shot at a title? How far do I have to get in rebuilding my roster before the deadline so I am ready for 2027? In at attempt to dig into some of this, I have been looking at 2025 roster and results data. I have a long series of questions I want to look into – how much is too much to spend on top players? Stars and scrubs or balance? – and today I am going to start with this one:
If you are trying to build a strong 2027 team, is it best to do that via keepers you held through the off-season? Players you trade for during the off-season? Or the auction?
I think this is a pretty useful question to answer right now because it impacts sellers and buyers. Sellers are already thinking about 2027 directly; but buyers are trying to determine how willing they should be to break apart their core to win right now. So they are also wondering how they can/will build a 2027 roster if they are giving up keepers today.
A couple of weeks back, I dug into how 
