The Boston Legal veteran officially joined the NBC series last month after making a guest appearance on the season finale in May.
Spader revealed that his character Robert California will be featured heavily on the series, appearing in nearly double the amount of episodes that his predecessor, actress Kathy Bates, featured.
"Robert California is there much more," Spader told Entertainment Weekly. "He doesn't have an office, really, he catches a desk where he can."
The actor went on to describe California, noting that he is still fleshing out the character's personality.
"He's a sort of strange guy, and his enigmatic qualities are a good thing," Spader said. "Everybody is trying to get to know who he is and what his juxtaposition is to the rest of the office. The characters are, and the writers and cast members as well. And I'm hoping that's going to be the fun of the season."
Meanwhile, there is no word on who will be replacing departing manager Michael Scott (Steve Carell), though it has been said that no new actors will be brought on for the role.
"They didn't just want to bring in a new Michael Scott, there's not an attempt to fill those shoes," Spader said. "That is something that I think they're allowing a certain amount of flexibility on, not unlike the end of last season. The show is very balanced right now and they want to utilise the ensemble cast."
The Office returns next month on Thursdays at 9pm on NBC.
Watch a video preview of the new season of The Office below: