I decided to experiment a little, since this error is annoying.
I downloaded the last version of file-roller, 3.3.2, in source code form, unzipped it and build it.
$ cd file-roller-3.3.2
Then I copied the executables in src to the following locations:
$ cd src
$ sudo cp file-roller /usr/bin
$ sudo cp file-roller-server /usr/lib/file-roller/
And now everything works as a charm. Drag & Drop is fully functional again. I know I should not install binaries this way, though this error is so annyoing, and has been unattended for so long as well, that I think that yes, it is justified.
So, the fix to the problem is to pack and the distribute the last file-roller.