The 19-year-old found the net twice in six minutes to give his side a relaxed lead, but substitute Adrian Lopez’s absent goal means the tie is far from around going into the 2nd leg in Portugal.
It took 38 minutes for the initial exertion of note to arrive as Edin Dzeko raced on to a clipped ball into the channel, reduce within a defender towards the edge of the six yard box and fired a highly effective shot off the near post.
Roma broke the deadlock by Zaniolo on 70 minutes when he raced on to a lay-off from Dzeko to fire into the corner.
Just six minutes afterwards he doubled his team’s tally and Dzeko was the creator again, firing a prolonged variety shot off the post for Zaniolo to faucet in and come to be the youngest Italian to score two goals in a Champions League match.
Nevertheless, Lopez latched on to an sliced shot and found the net with 10 minutes remaining to give his side a lifeline in advance of the 2nd leg on Wednesday 6 March in Portugal.