Leitrim-Roscommon

My ancestors Francis Duke and Elizabeth Gilland (Eliza) emigrated from Clune (Cloone?), Leitrim to Ontario, Canada in 1830, settling in Marlborough Township. Their religion was Church of England/Church of Ireland. Most, if not all, of their children were born in Leitrim, although the only specific date I have is for their son, John Erasmus Duke, born Feb. 11, 1824. My GGGG grandmother is their daughter Ruth, born about 1821.

I'd be very grateful for any suggestions on how to get more information on Francis (who was a Sergeant in some kind of military unit) and Eliza and their own ancestors. I'm in NY, and not planning any Irish trips any time soon...

best,
Suzanne