"I am really excited to have Brian join our staff," Fisher told the team's official website. "He is a well-respected coach in this league who has had success for many years at a high level as an offensive coordinator. We share the same philosophies on the offensive side of the ball, and I think he is a tremendous addition to our staff."
"He brings an aggressive approach that I'm sure will benefit our defense, and he has a wealth of knowledge that will aid our entire team." Fisher said of Williams on the team's website.
Schottenheimer also is joining the Rams' staff for the second time after working as an offensive assistant under then-coach Dick Vermeil in 1997 in his first NFL coaching job.
The Associated Press contributed to this report.