During the riot instigated by Franky Doyle, Rosie goes into premature labour. Meg helps Rosie until the others realise Meg's presence and take her hostage. Rosie is released before long, when Franky is warned it's in her best interests. After this ordeal, Rosie is eventually sent to hospital to have her baby, a boy named Sam.
Rosie is eventually transferred to the maternity wing, and we don't see her again until Episode 070, when her baby Sam was reaching the age of one. Rosie was in denial about her baby being taken away and looked after by foster parents (something that happened to all pregnant prisoners).
When the baby does get taken away, Rosie suffers a breakdown. She later believed Chrissie Latham (who was already pregnant and in maternity), had something to do with Sam being taken away, and punched her in the stomach. Luckily for Rosie, it has no effect on Chrissie's baby.