Excluding loanees*, it is easier to say who Robins would definitely keep - there are only three (with three other possibles).
Keep: Dabo, Hamer, O'Hare. And even then if the right offer came in...
Possibles Walker (potential) MacFadz (until his legs finally go) Wilson (you need a second string goalie; he's as good as you get for the position)
Thereafter any of the rest are dispensable as not one of them is definitely top half Championship calibre. Sorry you poor deluded fools, Godden, Max, Kelly, Hyam, Rose, JJ, Marosi, Shipley, Allen, are all just not good enough to form the core of a side hoping to be above halfway in the Championship. Peripheral squad players at best.
But you would not get rid of all of them at once, so who leaves maybe kind of random depending on who we are looking to acquire and who has another club interested. The out of contract peripherals like Baka are obvious departures, but who knows who else might move?
There probably needs to be a clear out at the Under 23 level as well as some like Bremang seeem to be long term residents there. They might get into the first team if we were still in League 2, but not the Chamionship. Our singular inability to loan some of them out is a clue.
Time for Robins to be as radical as the budget allows. Some will stay but you will never get far with a side with so many makeweights.
* By my reckoning James, Gyokeres, Sam Mac, Sheaf and Osti