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

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