Roberts and Johnson's clients also include U.S. Senator Rick Scott of Florida, the National Republican Congressional Committee and the National Republican Senatorial Committee, the firm said.
Musk and spokespersons for Johnson, Scott and Ramaswamy did not immediately respond to requests for comment.
Other conservative law firms with ties to Trump's inner circle include Dhillon Law Group. Trump named founder Harmeet Dhillon to head the Justice Department's civil rights division and partner David Warrington as his White House counsel.
Another is Schaerr Jaffe, which Musk has tapped to represent X users in free speech cases. Trump appointed Schaerr Jaffe partner Mark Paoletta as general counsel to the U.S. Office of Management and Budget, a key agency in the drive to shrink the federal government.