Just to throw an extra spanner in the works... there is no reason why an HD drive shouldn't work in your Roland, but it would function as a 720.

It will not recognise HD floppies, but should read and write 720s okay. The only problem would occur when writing to disks that aren't blank, because HD 'tracks' are narrower than 720 tracks. This problem would only be apparent, though, if you tried to then read the floppy with a 'real' 720 drive, because there would be two lots of information per 'track'.

You would get 'general failures' if you tried to use an HD floppy without the hole blanked off, though.