Born in Oceanside, New York, and raised in Newburgh, Indiana, Rosenbaum excelled in high school drama classes. Once hooked, he took on lead roles in college stage productions such as The Heidi Chronicles while attending Western Kentucky University and performing in regional theater during his summers.

Upon graduation with a degree in Mass Communications and Theater, he packed his bags and headed for New York to pursue acting. He quickly landed roles in off-Broadway productions and small independent films. His first real break came when he got a series regular role on The WB comedy series The Tom Show, with Tom Arnold. The relationship with the network continued as he was cast as Jack in the New York comedy Zoe, Duncan, Jack & Jane. Keeping busy over his hiatus, Rosenbaum appeared in the feature film Bringing Down the House, opposite Steve Martin. He can be seen in the independent film Poolhall Junkies, with Chazz Palminteri and Christopher Walken. Other film credits include Sorority Boys, with 7th Heaven's Barry Watson and Sweet November with Keanu Reeves and Charlize Theron. He also starred in the hit thriller Urban Legend and appeared in Midnight in the Garden of Good and Evil, directed by Clint Eastwood and starring Kevin Spacey and John Cusack.

When not working, Michael belongs to an ice hockey league, a sport that he has played since childhood, and is a dedicated New York Rangers fan.