Rosen rejoins Spamalot after a recent run in The Farnsworth Invention, Aaron Sorkin's play about the creation of television, in which he appeared alongside another Spamalot alum, Hank Azaria. Rosen is also the co-creator and host of Don't Quit Your Day Job, an after-hours improv-comedy variety show featuring Broadway actors.

Rosen returns to a cast headed by Jonathan Hadary as King Arthur and Hannah Waddingham as the Lady of the Lake. They are joined by American Idol star Clay Aiken, Tom Deckman, Rick Holmes, David Hibbard and Bradley Dean.

Spamalot features a book by Eric Idle, who co-wrote the music with John Du Prez, and is based on the screenplay of Monty Python and the Holy Grail by Monty Python creators Graham Chapman, John Cleese, Terry Gilliam, Eric Idle, Terry Jones and Michael Palin. Directed by Mike Nichols, it also features choreography by Casey Nicholaw.

The production won the 2005 Tony Award for Best Musical, the 2005 Drama Desk Award for Outstanding Musical, and the 2005 Outer Critics Circle Award for Outstanding Musical.