The Giallorossi have won all eight of their league games so far, including impressive victories over the likes of Inter and Napoli in recent weeks.
But Lopez believes his new team can overcome his old employers when they clash at the Friuli this weekend.
"Roma are a very strong outfit, who are looking to finish first and win everything," he told the club's official website.
"They have been playing a perfect championship so far. We will face them on Sunday and I think we can play a good match and win the three points.
"I hope I get to play and score."
Lopez has made just three appearances for Udine, who current sit 11th in the table, having lost half of their opening eight games.