The former Miss Ireland announced on Facebook: "Rob & I are so happy to be expecting a baby, feeling blessed."
She thanked everyone who had sent her "lovely messages" following the announcement.
The Ireland AM fashion correspondent has presented fashion slots on the television breakfast show weekly since retiring from full-time modelling five years ago.
The Clonmel native and her businessman husband got engaged at the Eiffel Tower in Paris in 2011 and were married at a glamorous ceremony in Ibiza last year.
She started the Andrea Roche modelling agency in 2010 and has launched the careers of some of the country's most famous models including Roz Purcell, Clara McSweeney and Pippa O'Connor.
She has also worked closely with 2003 Miss World Rosanna Davison.
Andrea took part in the RTE One reality sports television series Celebrity Bainisteoir in 2009.
Andrea retired from modelling in 2008 and has achieved big success with her model agency. In the same year, she won the VIP Most Stylish Woman award at the VIP Style Awards.
The bridesmaids at Andrea and Rob's wedding included her new sister-in-law TV star Holly White and PR businesswoman Tara O'Connor.
Tara O'Connor, Andrea's close friend, is also expecting a baby. She and her husband Andy Reynolds are thrilled.