USS Roanoke, a 4772-ton steam frigate built at the Norfolk Navy Yard, Portsmouth, Virginia, was commissioned in May 1857. For the next five months she served with the Home Squadron along the U.S. east coast and in the Caribbean. Her primary duty was transporting the adventurer William Walker and over two hundred of his men from Nicaragua to the United States. Out of commission from late September 1857 until mid-August 1858, Roanoke then became the Home Squadron's flagship, mainly serving in the West Indies and off Central America. In April and May 1860, she brought a Japanese diplomatic delegation from Aspinwall, in what later became Panama, to the U.S. Again decommissioned at the end of that voyage, she did not return to active service until June 1861, when she was needed for Civil War employment.

Roanoke enforced the blockade during much of the rest of the year, helping to capture or destroy four sailing vessels off North and South Carolina between mid-July and mid-October. She was stationed in Hampton Roads, Virginia, in March 1861, when the Confederate ironclad Virginia attacked Federal warships there. However, her deep draft prevented her from engaging the enemy. Later in the month, Roanoke went to New York, where she was decommissioned. In a project inspired by both the Virginia, which had originally been a very similar steam frigate, and the pioneer turret ship Monitor, Roanoke was then taken in hand for conversion to a very large triple-turret ironclad.