Bottom clubIngolstadt's win against the side coached by their former boss Ralph Hasenhuttl lifted them off the foot of the table and did a favour to their Bavarian rivals Bayern Munich, who replaced Leipzig at the top of the standings.
Leckie saw red after being booked twice, the second of his yellow cards coming in stoppage-time.
The only goal of the game came in the 12th minute when Roger rose to get a decisive flick on Anthony Jung's free-kick and divert the ball past Peter Gulacsi into the far corner of the visitors' net.
Marcel Halstenberg should have brought Leipzig level after 20 minutes, but he contrived to send the ball wide of the post when it seemed easier to score from close range.
Emil Forsberg was put through on goal 10 minutes before half-time, but while he did hit the target with his effort, goalkeeper Martin Hansen was equal to it.
Leipzig picked up in the second half where they had left off in the first with Forsberg again going close to grabbing an equaliser in what was becoming a siege on the Ingolstadt goal.
Leckie could have dented their hopes when he beat the offside trap but, at full stretch, he sent his shot wide of the near post with 15 minutes remaining.
Those 15 minutes also belonged to Leipzig, but it became clear that it was not going to be their afternoon when Forsberg uncharacteristically shot wide from six yards.
Leckie picked up a second yellow card in a fiery five minutes of stoppage-time - but Ingolstadt held on.