where are the ROMS??
Which person decided that was a good idea?
Recalbox only has some pre-installed ROMS that are freeware or that the author has authorized the distribution.
These ROMS are not in the same folder that the user accesses, and an option was added to hide them easily because many users complained that they already had the ROMS they wanted and didn't want to have to delete the pre-installed ROMS with each update.
If you connect your SD card to a PC with the help of a USB adapter, you can access the folder with ROMS and add and/or delete your own ROMS.
It is also possible to connect your Rpi to the network via cable or via wifi, and access the folder with the ROMS via SSH (I recommend using WinSCP).
The option to delete ROMS directly from the Recalbox menu has been removed to avoid some critical Emulationstation failures, we still don't know if this will be definitive or not, there are several factors that influence this decision.