Hi @iainduncan,
the Sonic Poi core team can be seen in the ‘Core Team’ tab of the info pane within the app itself.
You can see a simple list here too: https://github.com/samaaron/sonic-pi/blob/master/CONTRIBUTORS.md#core-team
With respect to a roadmap, this is something we’ve never had as a formal thing. There are many ideas we would all like to work on, but typically for an idea to make it into Sonic Pi it needs at least the following:
- A personal reason for it existing (we want features to be meaningful to the people that work on them)
- A broader more interesting reason for it existing (how would it benefit other users)
- For the feature to tesselate well with existing features
- For it to be simple enough to teach to a 10 year old child
It’s typically the last constraint which is the hardest to meet 
If you have any ideas that you think may pass these constraints, please do bring them up here and we’d be very happy to discuss them, flesh them out, and be positive and constructive about it.
Looking forward to your thoughts!