Rosler, who was officially announced as the new man in charge on Saturday morning, was in the stands as the Latics were undone by strikes from Steve Morison and Jermaine Easter.
James McArthur pulled back a goal late on and the visitors pushed hard for an equaliser, only to fall narrowly short and leave them in 14th in the Championship table.
But despite the poor run the club are on that cost Owen Coyle his job, Barrow insists with Rosler's help in the striking department there is much to look forward to.
"Uwe isn't walking into a club in free fall because as we've shown here there's a lot that is right," he said.
"I think it's just the attacking side which needs working on and with Uwe having been a top striker maybe he can help us with that and the movement of the players.
"Uwe came in the dressing room before the game, at half-time and full-time and he will be in the club tomorrow.
"He seems a very positive man and I'm looking forward to working with him.
"I believe I will be staying. I had a brief chat with him on the phone on Friday night and he said he was looking forward to working with me.
"The whole club is excited about Uwe coming in. The players have been great all along but you could tell that they'd been given a lift.
"You never stop learning from people so there are things I learnt from Roberto [Martinez] when he was here and hopefully I can do the same from Uwe."
For Steve Lomas' Millwall troops it was a seventh game unbeaten at the New Den although the manager admitted his side had made it harder than they needed to.
"There was always going to be pressure at the end," he said.
"We like to make things difficult for ourselves. At 2-0 you think the game has been put to bed and then they get a chance straight away and then we were just hoping we could withstand the pressure and we did.
"It would have been unjust if we didn't get the three points.
"Wigan had a right go and they've got some good professional players there. We knew with their quality they would probably have quite a bit of possession but were always a danger on the counter."