Barca suffered a shock 2-0 defeat at the San Siro last night to leave their hopes of winning the tournament in tatters.
“We struggled to find depth and to reach their goal,” said stand in coach Roura.
“Obviously this wasn't our best game. Although we had problems I think that the result is excessive.
“They found a couple of opportunities and scored from them which now makes things tricky for us.
“We all know how difficult it is in this stadium. They have defended with everything behind the ball, very orderly. We struggled to find depth.
“The comeback will be difficult, it is two goals, but we have confidence, for our players, for our stadium.
“It will be a different story in the second leg. We fully believe we can turn this around.”