I’ve got a couple of the new wireless Sega Genesis/Saturn-style 6-button-controllers from 8bitdo and Retrobit. Unfortunately, none of the Bluetooth controllers are automatically detected and properly configured inside of RetroArch. I manually have to rebind the buttons to have the C, Z, LB and RB working inside Sega games as expected.
You can generate your own autoconfig (and, optionally, submit it for future inclusion in RetroArch). Go to settings > input > user 1 binds. Hit ‘default all’, then ‘bind all’, bind all of the buttons, save autoconfig, hit default all again and then quit retroarch. When you open it again, it should recognize and automatically configure your pad.