Rosler believes the Foxes, the Sky Bet Championship leaders who have a 15-point advantage over third-placed QPR, are certainties to be playing in the Premier League next season.
Because of that he feels the pressure is off the play-off chasing Latics in Tuesday's meeting of the two sides at the DW Stadium.
But Rosler still wants the FA Cup semi-finalists, fifth after Saturday's draw at Bolton, to push hard in what is a game in hand on their rivals.
Rosler said: "We have put ourselves, at the beginning of April, in a really good position but now we should not make the mistake of trying to defend our position.
"I think this is a bonus game for us, the game in hand. It is a game where we can increase the gap between us and our competitors.
"I desperately want to get something out of the game.
"In the position we are in, and how tight this league is, we have to make sure we are in the top six. That is the priority.
"Leicester are on a very long unbeaten run and they will come here not wanting to give that up easily.
"They want to win the league. It is not about winning promotion any more - they are already promoted.
"But it will be a very good contest. I think we have more than enough to give them a really good game."
Leicester, unbeaten in 19 games, took themselves within seven points of a top-flight return with eight games remaining as they beat second-placed Burnley 2-0 at the weekend.
With eight games to play, their task seems straightforward.
Wigan, who scored a late equaliser at Bolton and then missed an injury-time penalty, still have much to do to achieve their objectives.
But Rosler is counting on strong support as his side begin a run of four successive home league games.
The German said: "At Bolton we had the best crowd I experienced - noisy, big numbers. They were supportive even when we didn't play well for periods.
"It was good to end the game on a positive and I think now the numbers will come again against Leicester and Leeds.
"I am really looking forward to the games."