ROSCOMMON, a county of Ireland, in the province of Connaught, bounded on the west by the river Suc, on the east by the Shannon, on the north by the Curlew mountains, on the south and south-east by the King's county, and part of Galway. Its length is 50 miles, its breadth 28. The air of the county, both on the plains and mountains, is healthy; the soil yields plenty of grass with some corn, and feeds numerous herds of cattle. The Curlew mountains on the north are very high and steep; and, till a road with great labour and difficulty was cut through them, were impassable. This county contains 59 parishes, 86,000 inhabitants, and sends two members to the imperial parliament. See ROSCOMMON SUPPLEMENT.