There were comments about Raspberry pi 2 support as an endpoint with RoonSpeakers by devs in these threads:
Definitely an early target at that stage. @brian may (or may not !) be able to say something further about it.
Edit: Auralic Aries Mini is a pretty interesting product with 192k/24bit Toslink out, not yet released though and will need RoonSpeakers before it can be a network endpoint.