Roundwood is located where the R755 road joins the R764 and R765. The R755 is part of the main route from Dublin to Glendalough in the Wicklow Mountains. At 238 metres above sea level, Roundwood is one of the highest villages in Ireland.
Vartry Reservoir Lakes (reservoirs built in the 1860s) are close by.
Roundwood has a close association with two former Presidents of Ireland, Seán T. O'Kelly who lived locally and Erskine Childers who is buried in the Church of Ireland Derralossary churchyard near the village.
Roundwood is twinned with the village of Spézet, in Brittany, in the northwest of France. The schools in both areas regularly communicate and engage with another. For many years, exchange programmes have been in place for the students.