You can place a newborn baby in a rocker or bouncer as long as you supervise them at all times.
Never put the newborn or other baby into a rocker or bouncer and allow them to sleep or without supervision.
It's okay for a baby such as a newborn to take a nap in a rocker or bouncer while you're supervising the baby but it's never okay to leave the newborn in the rocker for the whole night.
A baby should always be in a bassinet or in a crib to sleep safely through the night and newborns up until at least 12 months of age should sleep on a firm mattress or firm surface without pillows, blankets or other soft toys.
If the newborn is allowed soft toys, blankets or pillows they could die of SIDS and suffocate.
Always supervise the baby in the rocker or bouncer.
It's okay to put the baby in the rocker or bouncer and then go into the kitchen or bathroom for a few seconds or so but never leave them longer than a minute or two alone in the rocker or bouncer.