Can an unvaccinated mother get rotovirus from a baby who just had roto vaccine through his mouth (through touching baby, s binky by mouth)?

Yes: If the mother of vaccinated infant is immunocompromised, she can get infected by vaccine virus since roto vaccine contains live virus.

Unlikely: Most adults have long since developed immunity to rota virus & such a minimal exposure would be unlikely to pass it to you. There is actually vaccine virus in the poop of every vaccinated kid that remains for up to 6 weeks after a dose. Even an adult with no prior exposure to the virus would be unlikely to become sick, since the vaccine is a weakened strain to begin with, not the wild virus.