If you want to expand your Roland TD-17 KVX2 or KV2 kit, use this hack to split the head and rim signals from one of your toms. This electronic drum splitter from drumsplitters.com allows you to add another cymbal, drum pad, or anything you want without needing an open input! These splitters are made specifically for Roland Vdrum kits, they're reasonably priced, and THEY WORK!!
https://drumsplitters.com/