In 1822 he served under Simón Bolívar and participated in the Battle of Ayacucho.

From there on, San Román participated in various battles during the first years of the Peruvian republican period.

Despite this defeat, San Román was awarded the grade of Gran Mariscal.

Miguel de San Román introduced the Peruvian Sol currency in 1863 and adopted the decimal system for standard weight and measures.

He died a couple of months after assuming power in the Lima district Chorrillos.