Roach emigrated to the United States at the age of sixteen in 1832, eventually finding employment at the Howell Works of James P. Allaire in New Jersey, where he learned the ironmolder's trade.

In 1871, Roach purchased the shipyard in Chester, Pennsylvania of Reaney, Son & Archbold, which had fallen into receivership, and renamed it the Delaware River Iron Ship Building and Engine Works, which thereafter became his main facility.

From 1871 until 1885, John Roach & Sons was easily the largest and most productive shipbuilding firm in the United States, building more tonnage of ships than its next two chief competitors combined.

John Roach was born on December 25, 1815, at Mitchelstown, County Cork, Ireland, the first of seven children to Patrick Roche,[2] a retail salesman, and his wife Abigail Meany.

[4][6] Roach began his employment at the Howell Works as a common laborer at 25c a day, collecting bricks and conveying them in a wheelbarrow to various building sites around the company grounds.

[10] Once in Illinois, Roach was dismayed to discover that so complete was the isolation of the region that corn served not only as the staple foodstuff, but also as the principal source of heating and even as the local currency.

[13] In 1852, Roach, by now 37 years of age, joined with three other ironmolders, including his brother-in-law Joseph Johnston who had $8,000 in savings (equivalent to $290,000 in 2023), to purchase a small New York ironworks which had fallen into receivership, the Etna Iron Works.

When the American Civil War broke out in 1861, Roach was in a position to take advantage of high demand by converting his plant into a manufacturer of marine steam engines.

[16] In the aftermath of the war, the U.S. government dumped more than a million tons of surplus shipping onto the market, depressing prices and leaving shipyards and marine engine builders with little or no work.

[17] Roach, however, managed to prosper in this difficult period by diversifying into the manufacture of machine tools, and selling them to the U.S. Navy which was in the process of upgrading the facilities of its own shipyards.

[20] This network of vertically integrated companies enabled Roach to largely eliminate third-party suppliers, cutting costs and thus allowing him to regularly underbid competitors.

He quickly established himself as the nation's leading iron shipbuilder, building more tonnage of ships in most years than the aggregate output of his next two major competitors, Harlan & Hollingsworth and William Cramp & Sons.

To Roach's dismay however, both the Brazilian and U.S. governments ultimately rejected his application for subsidies, and his Brazil Mail company struggled on for a number of years before eventually failing.

[23][24] Roach lost almost a million dollars ($29,000,000) in his Brazilian shipping line venture,[23] leading to a shortage of operating capital for his business empire that would eventually contribute to its financial failure.

While Roach may indeed have benefited from a degree of favoritism under Republican administrations, no credible evidence was ever presented to substantiate the allegations of corruption made against him, and indeed his ability to regularly undercut his competitors sometimes saved the government considerable sums of money.

The first substantial political controversy in which Roach was engaged arose from his sale of surplus machine tools from the Etna Iron Works to the Philadelphia Navy Yard in 1867.

In support of claims that the contract had been awarded as a result of political favoritism, Kelley produced two compliant experts who were prepared to testify against the quality of Roach's tools.

[25] The investigation soon drew the attention of the Navy's Bureau of Steam Engineering, Benjamin Isherwood, who appointed a board which took evidence from 25 independent experts on the quality of Roach's machine tools, and which unanimously repudiated the findings of the Kelley report.

Roach quickly began work on the contract, but in 1873, Pacific Mail confessed an inability to meet its obligations after the company's managing director squandered its capital reserves with a failed stock manipulation scheme and then absconded with a large amount of cash.

The situation was made worse when stock speculator Jay Gould, in an attempt to gain control of Pacific Mail by driving down its share price, lobbied Congress to cancel the $500,000 subsidy it had earlier granted to the company.

Two days before leaving office, he gave orders for completion of the monitors and at the same time awarded a further $997,000 contract to Roach for the addition of armored belts and turrets to Puritan.

The board concluded that the work Roach had done on Puritan was first-class, and that the price of the contracts had been reasonable; however, it averred that the extra weight of the armored belts would render the ship unseaworthy.

[38] The Puritan controversy revived the attacks on Roach alleging favoritism and jobbery, and he was forced to keep the uncompleted vessel in his shipyard at his own expense for the next five years.

The following year, Roach decided to revive the company, believing that with the deployment of modern iron-hulled, screw-propelled steamships, he could succeed where the Garrison-run operation had failed.

Unfortunately, his high-profile campaign had the opposite effect to that intended, as a host of entrenched interest groups—including Bostonian sailing ship owners and merchants, free traders, and competitors in the shipbuilding industry—joined forces to oppose it.

Hunt conducted a review and found that the Navy at this time comprised a mere 52 seaworthy vessels, only 17 of which were iron-hulled, including 14 dated Civil-War era ironclads.

Appalled at the Navy's dilapidated condition, he appointed an advisory board in June 1881 to look into the problem, which made some recommendations concerning the desirable qualities for a new generation of warships.

Editor of The Sun, Charles Dana, seized upon this article to renew the attack upon Roach, and the various faction-ridden departments in the U.S. Navy began to circulate their own criticisms.

Americans ought to be proud of Roach, who started in life as a day laborer and became the giant of industry and the greatest shipbuilder in the United States ... What has he now for forty years of incessant work and worry?

[56] At his funeral, held at St. Paul's Methodist Episcopal Church on Fourth Ave. and Twenty-second St., 500 mourners filled the galleries alone, many of them employees of John Roach & Sons who demonstrated a "real affection" for their late employer.