He obtained a cadetship in the British East India Company's service in 1818, and on 11 April 1819 was commissioned as lieutenant in the 13th native infantry, Bombay establishment.

Following the annexation of Cutch by Company, the amirs of Sindh encouraged the Khosas and other tribes to make incursions in region.

He was soon afterwards employed politically, as assistant to the resident, and succeeded in establishing order and peace among the inhabitants of Thar, the district to the north of Cutch, who had hitherto been inveterate robbers and cattle-lifters.

After three years' furlough in England, Roberts was selected to raise a regiment of irregular cavalry in Gujarat, which he commanded till 1841.

In May 1843, he was ordered to march towards Indus to Schwan, with fifteen hundred men, for battle against Mir Sher Muhammad Talpur.

There he learnt that the brother of Sher Muhammad, with three thousand men, was encamped at Pirari, fourteen miles to the west.

One brigade of his force was then detached to assist Sir Hugh Rose, and the remainder was divided between Nimach and Nasirabad to cover Rajputana against inroads from the east.

On the 14 August, Roberts again came up with him, drawn up in position on the Bamas, and defeated him, taking his guns and killing about a thousand men.