Looking for Dempsey in Roscommon

Hello, I'm looking for my great-grandfather, Martin Joseph Dempsey, who was born around August, 1866 in Ireland, and immigrated to the US around 1883. I found an obituary for his brother, Michael, that said he was a native of Cloonfree (sp?), Strokestown, Roscommon.  I don't know who his parents are or anything else about the family.  He married Winnifred Mary Ryan in San Francisco.  Winifred was also born in Strokestown, Roscommon around August, 1860.  Her parents were Thomas Ryan and Winifred Mc Laughlin. That is all I know about either of them, and would be so grateful to receive any information on them!  Thank you so much!

Debbi Lawson

California