For anyone who may still be coming across this... Much of the content from roland-arranger.com is available in the internet archive. The following page links to most of the forum posts. Of the 8 pages of them, all are accessible except page 4. Not all the individual topics on each page are accessible, but 15 out of the 18 I tried were.

https://web.archive.org/web/20201019152839/http://www.roland-arranger.com/index.php/music-related