Ukić is a former member of the Croatian junior national teams, earning with them a gold medal at the 2002 FIBA Europe Under-18 Championship, and he also played with Croatia's junior national team at the 2003 FIBA Under-19 World Championship in Greece, averaging 19.8 points, 4.6 rebounds, 4.4 assists, and 2.6 steals per game, as his team reached the tournament's semifinals.[28] He has also been a member of the senior men's Croatian national basketball team. Some of the tournament's he has played in with Croatia's senior national team include: the EuroBasket 2005, the EuroBasket 2007, the 2008 Summer Olympics, the EuroBasket 2009, the 2010 FIBA World Championship, and the EuroBasket 2013. From 2010 on, he is the Croatian national team's captain. With 1,471 points scored (as of September 2014), he is 3rd in the list of all-time top scorers for the Croatian national team.[29] He also represented Croatia at the EuroBasket 2015,[30] where they were eliminated in the eighth finals by the Czech Republic.[31] He also played at the 2016 Summer Olympics.

Ne nekoliko ovih natjecanja, koliko ja znam, je Roko igra ozlijedjen i pod injekcijama, tako da ne znam baš da se nije žrtvova.