Latics last week acquired the 20-year-old from Chelsea until the end of the season but he missed the weekend win over Crystal Palace as Rosler instead focuses on getting him up to speed.
In the victory over Palace, which stretched Wigan's unbeaten FA Cup run to 10 games, central midfielder Ben Watson and winger James McClean scored while Roger Espinoza, another midfielder, set up both goals.
Given strikers such as Grant Holt, Marc-Antoine Fortune and recent recruit Nicky Maynard have struggled in front of goal, Rosler is pleased with how his midfield now looks.
"Josh is not ready now but he will be ready in a couple of weeks," Rosler explained.
"He will undergo a special programme and I think he offers us something that we will need. We need to feed our central striker with more opportunities to score goals.
"In the wider areas we look strong but we need to feed Nicky Maynard with quality balls like Jordi Gomez can play, like Josh can play. We're getting good competition and good options in midfield."