This is ridiculous. 11-year old trains being sent for long term storage. Something has to be done about this.
It's up to the owner (the Rosco) to find a customer willing to pay for a commercial lease.
What you may not realise, is that for some fleets the SRA/DfT committed to long-term leases (eg for class 350/1).
In order to transfer more risk from the DfT to the ROSCOS, DfT stopped long-term lease commitments (eg for classes 350/2 and 379).
Therefore DfT has no obligation to "bail out" the ROSCOS by re-leasing those trains, as it's not a DfT risk.
You'll find plenty of posts in these threads talking about ROSCOS "ripping off" the railway in the past, and this is the DfT getting its payback.
That's why 350/1s are staying and 350/2s are not.
Having said that, DfT wants the EMU fleet at the lowest cost going forward, and to dump old stock which is expensive to maintain, so may yet do a deal where it makes sense.
No TOC has yet been allowed to order any new EMUs since Covid arrived.