I've never had an actual "team" and from what I've been seeing teams rarely work in ROM hacks. ROM hacking is a hobby and it's hard for people to be there to help with things during the whole time it's developed, if you're lucky enough to find any that are willing to help. I've had a few partners that I would talk about my ideas with and ask for their opinions, and they would also help with hacking things too, but people eventually lose interest or leave. Maybe it's just me working slowly, but it is a hobby after all.
If you have people willing to help or join your team, my advice would be not to expect them to give you feedback on the other work you do as well. They will if they want to, but in my opinion, doing what you ask them to for the hack, be it music, graphics or anything else, is enough.
I believe you can still work on your own and get the things you can't do yourself done by other people (whether they're in the team or not) who offer to help. And if you need feedback on your work and ideas, remember that your hack has a lot of fans that would love to help with that by posting in this thread.
Good luck!