The versatile midfielder has conceded that the Azzurri had a difficult match as their opponents' physical approach caused them problems
The Azzurri recorded a 2-0 win, thanks to goals from Antonio Cassano and Mario Balotelli, to book their ticket for the knock-out stages, but the Roma player conceded that it was by no means a convincing performance.
"We struggled in this game, perhaps more than in the previous two. We couldn't find any space as they closed it down well," De Rossi told reporters.
"The Irish are a good team, very physical. They definitely made it a very difficult game, so they deserve credit for that.
"They play a good long-ball game and all you need is one mistake, one good moment for them. It's not easy when all of their side are so physical."
Italy will meet the winners of Group D in the quarter-finals.