The 45-year-old feels the fixture list has been unkind to his side but is confident about Lionel Messi's recovery from a hamstring problem
The Liga leaders will also be without stars such as Lionel Messi Andres Iniesta, Sergio Busquets and Jordi Alba for the trip to La Romareda and the 45-year-old feels exertions both in Spain and Europe are taking their toll.
"The fixture calendar has been horrible. As a result, we've been struggling a bit," he told reporters on the eve of the game.
"We've been unfortunate to have a lot of injuries, many of them serious ones. We've just had a really hard Champions League match, and have many players out injured and others in need of a rest.
"Despite all these difficulties however, we've managed to come through it all. Now it's back to business in the league, which is obviously really important and is our number-one objective.
Messi featured half-fit against Paris Saint-Germain in midweek and although he is missing the Zaragoza clash, Roura is optimistic that he will recover soon.
"We both hope and believe that he'll have recovered for the first leg of the semifinals," he continued.
"We'll have to see how he progresses. Fortunately, the injury was not made worse [against PSG]. He's working really hard and doing everything he can to get back on track."
The Catalans will travel to Allianz Arena to take on Bayern Munich on April 23 and Roura is expecting a classic.
"All the teams are tough at this stage. I think we have been the two best teams in Europe over the last few years."