The Gunners won the first leg 1-0 last night after a penalty goal by Robin van Persie.
“Arsenal played very well tonight, especially in the first half of the game,” Mexes confessed in an interview with forzaroma.info.
“But I am convinced that in the return leg you will see a different Roma.
“We have a lot of confidence in ourselves to attain a positive result and move forward in this competition,” he added.
“The penalty was probably there, and I got in front and made a mistake by taking out his feet.”