The Gunners made it two wins from two matches in Group F on Tuesday as they saw off Napoli 2-0 at the Emirates Stadium.
With the Germans up next for Arsenal, Ramsey is confident that his side can pick up some vital points.
"I think the games against Dortmund will be massive," the Welshman is quoted as saying by the Daily Star. "They are a tough team to play against and they got to the final last year but we're at home and we'll be confident of getting the right result against them.
"If we do we will put ourselves in a really positive position."
Ramsey has scored eight goals in 10 appearances for Arsenal so far this season.