The battle of Rosillo, known also as the battle of Salado and as the battle of Rosalis, was fought on March 29, 1813, on a prairie near the confluence of Rosillo and Salado creeks, nine miles southeast of San Antonio in southern Bexar County. The engagement was between the Republican Army of the North led by José Bernardo Gutiérrez de Lara and Samuel Kemper and a Spanish royalist force under Texas governor Manuel María de Salcedo and Nuevo León governor Simón de Herrera. The battle was called the battle of Salado in contemporary accounts but is generally known today as the battle of Rosillo to distinguish it from the battle of Salado Creek, sometimes called the battle of the Salado, in 1842. The battle of Rosillo resulted in the capture of San Antonio and the establishment of a first "republic of Texas."
After lifting a siege lasting from November 7, 1812, to February 19, 1813, against the republican forces of the Gutiérrez-Magee expedition at Presidio La Bahía, Spanish royalist forces under Salcedo and Herrera retreated to San Antonio. In mid-March the republican army, variously estimated at 600 to 900 men, set out along the road from La Bahía to San Antonio. A Spanish royalist force variously reported to be 950 to 1,500 men prepared an ambuscade along a ridge that borders the creeks. About eleven o'clock on the morning of March 29, the republicans were marching on the lower or mission road, expecting to find food and take up quarters for the night at San Francisco de la Espada Mission, when their flankers discovered the enemy on the upper road. The ensuing battle was bloody and brief, lasting no more than an hour but resulting in the complete rout of the royalists and the capture of most of their arms and ammunition, six cannons, and 1,500 horses and mules. Royalist losses were heavy, estimated to be 100 to 330 men, while the republicans lost only six men. The defeated royalists retreated to San Antonio, and the victorious republicans spent the night at Mission Espada. The next day they took up quarters at Nuestra Señora de la Purísma Concepción Mission. On April 1 Kemper marched his troops in battle formation to the gates of the city, where they were met by three envoys carrying a flag of truce. Governors Salcedo and Herrera surrendered unconditionally, and the Republican Army of the North took over the city.
An aftermath of the battle occurred on April 3, when Salcedo, Herrera, and twelve other prisoners were escorted late that evening out of Bexar under the guard of sixty men and were brutally executed near the site of the battle of Rosillo. A declaration of independence was adopted on April 6, 1813, establishing a republic of Texas with Gutiérrez as president, a Junta de Gobierno, and a constitution. All came to an end after the disastrous battle of Medina on August 18, 1813. In 1992 neither the site of the battle of Rosillo nor the site of the executions of governors Salcedo and Herrera had been archeologically confirmed.