The England U20 side demolished Nigeria 8-1 in their first match of the Continental Cup in South Korea on Wednesday.
The Young Lions pounced on the African side with four goals in the first half before adding a further four in the second lot of 45 minutes at the Suwon Sports Complex.
Captain Taylor Moore, of Bristol City, opened the scoring in the 19th minute before Armstrong added a second only moments later.
Chelsea talent Dom Solanke made it 3-0 on 25 minutes prior to Armstrong's second two minutes later, making it four goals in a devastating eight minutes.
Nigeria managed to get one back in the 35th minute through Abdulrazak Yusuf but it accounted for nothing as England continued their demolition job in the second half.
Everton defender Callum Connolly made it 5-1 a minute into the second half before Roberts got in on the act in the 49th minute.
Armstrong completed his hat-trick with 20 minutes remaining to make it 7-1 before Roberts wrapped it up in the 87th minute.
The Young Lions will next meet hosts South Korea on Friday before rounding out the min-tournament against Iran on Saturday as they continue their preparations for the 2017 FIFA U20 World Cup in South Korea next summer.