There’s just one John Leddy listed in Annagh parish in Griffiths Valuation in 1857. He was living in the townland of Rosskeeragh, which is a mile or so south of Belturbet on the modern N3. Rosskeeragh is a rural area adjacent to Drumavaddy townland. John was renting plot 19 which was a house and 3 acres (subsistence farming). You can see it on the Griffiths maps:

http://www.askaboutireland.ie/griffith-valuation/index.xml?a...

There were 9 households in the townland in the 1901 census. Nonew as named Leddy then.

http://www.census.nationalarchives.ie/pages/1901/Cavan/Grill...

I would next search the parish records, if they go back that far, to determine whether this is the correct family.