Dortmund sold Ousmane Dembele to Barcelona for €105 million (A$156.86 million) but the club were then able to bring in Andriy Yarmolenko, Jeremy Toljan and Jadon Sancho late in the transfer window.
While Bosz acknowledges this gives him a selection headache, the Dortmund coach believes he will need to use all of the players at his disposal over the course of the season.
"We will need more than just 11 players in the coming weeks," Bosz told a pre-match news conference ahead of facing Freiburg.
"We will need everyone. We have a large squad, so we should use it."
He added: "It will not be easy for some players, but there have been no issues yet."
Bosz confirmed that all of his international players had returned unscathed, before offering updates on his new men.
"Yarmolenko has not trained with the team yet," he said. "But we know him well. He was the best option for Dortmund.
"I don't know yet if he will be ready for the match. I'll talk to him [on Friday], but he's definitely fit.
"Toljan just needs to adapt to our style of play. He was in full training with Hoffenheim, so he is match fit.
"But Sancho hasn't trained for quite some time - he needs to build up stamina. He's still got a long way to go."