In November 1857 Rockwell was involved in an attack on a half-dozen Californians known as the Aiken party, who were attempting to reach U.S. troops wintering at Fort Bridger. Twenty years later, Rockwell would be indicted on two counts of first-degree murder in the deaths of John and William Aiken.

By the spring of 1858, Brigham Young agreed to amnesty terms offered by President Buchanan, and the Utah Expedition, commanded by Brigadier General Albert Sidney Johnston, proceeded to establish Camp Floyd south of Great Salt Lake City. After the outbreak of the Civil War, Colonel P.E. Connor, who was ordered to Utah with the California Volunteers to "protect the mails from Indian depredations," hired Rockwell as a guide and scout for infantry and cavalry in an action against a band of Shoshones at Bear River near present Preston, Idaho, in January 1863.