I personally think this is the right approach.
I wrote a walkthrough (five years ago!) on how to run Roon in Docker on Synology. In the walkthrough, I proposed a folder structure for container-based Roon and suggested that the first step was to get existing Roon backups copied over to that folder. One way or another, you need to get existing backups to be visible to the container and this seemed like the simplest path.
I wrote the walkthrough before Synology supported compose files (which is what they call “Projects”). It’s tempting to think about moving from the wizard-based configuration over to Projects, but there are tradeoffs. If the new container requires or prefers image updates for app updates, then it’s probably better to stick with the single-container wizard approach because Synology is much better with image updates when not using Projects (individual containers get update notifications and single-click updates, Projects get no notifications and a complex, multi-step update process).
I’m hopeful that we’ll get great guides from Roon on how to get containers stood up on Synology and QNAP as well as how to update images. Until then, my old guide is probably a pretty good reference for how to do it on Synology: