Only the DJ70 mkII have a SCSI interface. Roland does not offer a upgrade for the DJ70.
An old document from Roland site (dated 1997) provides a company in Italy that does SCSI modifications, but maybe this information is outdated.
Look for the DJ70 supplemental notes at:
http://www.rolandus.com/SUPPORT/DOCS/SUPNOTES/DJMKII.HTM The same document also in Adobe Acrobat format:
http://www.rolandus.com/SUPPORT/DOCS/SUPNOTES/DJ70SN.PDF Mgomes