Yes, you can make crochet edges using your Janome 15000. This video from onlinesewing.com shows you how to make a crochet edge using an Heirloom Stitch on the Janome 15000. You can experiment with different stitches. If you have not checked out onlinesewing.com you might want to take a look at this very informative website.
Cindy Losekamp (www.sewingart.com) produced a wonderful workbook a few years ago (2006). The book shows you how to use a range of stitches to make unique edgings. While the book is written using the Janome 11000, 10001 and 10000, it is fairly easy to translate the stitches to those stitches on the Janome 15000.