The Gunners lost the first leg 3-1 at the Emirates Stadium meaning they have to win by three clear goals on Tuesday.
Arsenal warmed up for their trip to the Stade Louis II by beating West Ham 3-0 in the Premier League and Ramsey is optimistic about their chances against the Principality club.
He said: “We need to score goals. So we will go there and try to score three or more goals and hopefully not concede any. That’s our target and that’s how we will approach it.
“We had a sloppy first leg and we’ve made it quite difficult for ourselves but it’s not over yet. We are more than capable of scoring three goals.
“We scored three today and we believe in ourselves. We’ll go into the game believing we can achieve that.”
“For us to progress, we have to play in the way we know we can.
“We want to disrupt their rhythm and try to score early.
“It’s going to be difficult to score three times as they have defended well in the tournament so far.
“But if you look at our past matches and the way we played against Manchester United last week, I think there’s a chance we can progress.”