Not in this case. It would be a conflict of interest, they are potential witnesses against each other.
The Clinton attorneys are assisting with Rosen's civil case. I think there are big conflicts of interest here, memorialized by Rosen's comments on tape.
This excerpt from an article in the NY Sun (5/9/05) is what gave me the idea that there is/was a common defense:
In an interview, an attorney for the Clintons, David Kendall, said he was confused by Mr. Rosen's statement. He said lawyers for the various defendants have made no effort to hide their coordination and have at times filed joint briefs.
"It's no secret that counsel for Mr. Rosen, the Clinton for Senate Committee, and the Clintons have been cooperating in the defense of a meritless civil suit brought by Peter Paul," Mr. Kendall said.