Juan Iturbe scored his first goal for the club from the penalty spot, while Gervinho, Miralem Pjanic and Adem Ljajic also found the net in Friday's clash.
Despite the emphatic nature of the scoreline, Garcia felt his side can still improve their potency in attacking situations ahead of the new Serie A season.
"Between this game and the last, we wasted so many chances," he told Roma Channel.
"We need to be more efficient in front of goal.
"When we face stronger sides, it's going to be much more difficult. I liked that Iturbe took on the responsibility of converting the penalty and it was a nice gesture from Miralem Pjanic to let him take it.
"This Austrian training camp has been positive, as we worked in an atmosphere of such wild enthusiasm from the fans.
"We'll need them this season and with them as our 12th man it will all seem easier."
