First found in Herefordshire, where they were seated from early times and their first records appeared on the early census rolls taken by the early Kings of Britain to determine the rate of taxation of their subjects. The form Rosser was found in Chancery, where a Morres Rosser was recorded in Wales in 1100, in the "Calendar of Proceedings in Chancery" published during the reign of Elizabeth I in the 16th century.

North America in the 1800s and 1900s saw the arrival of many Welsh people hoping to share in the wealth of land, work, and freedom that they felt North America held. Those who made the journey often attained those expectations, but only through an enormous amount of hard work, perseverance, and often a bout of good luck. These immigrants helped contriBute to the growth of industry, commerce, and culture of both Canada and the United States. Discovered in the immigration and passenger lists were a number of people bearing the name Roser: George Prosser settled in Virginia in 1635; along with Jane; Thomas Prosser settled in Barbados in 1634; William Prosser settled in Virginia in 1654;Hugh Rosser came to Maryland in 1665.

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