Unknown Parish

All I know Is Robert Dillon was born in County Roscommon In about 1822. I found his grave In Holland Wisconsin and he died In 1857,no death record.They left Ireland in 1841 or 42, first arrived in Nova Scotia,then I found them In the 1850 and 1855 Mass censes.Then found them in 1857 -1865 In Wisconsin,then Michigan and Minnesota.He was married to Rose Early had son John In Ireland,then Thomas,Bridget and Ellen In Mass.When they lived In Mass In 1850-1855,they were living with a Thomas Dillon, who seem's to be a twin of Robert's as they were the same age.Thomas was with his wife Bridget,Who I believe her maiden name to be Fallon,also with them was a William Fallon and a Michael Dillon.I hired a Genealogist In Ireland and he checked all church record's but they were not to be found.Also checked Griffith also with no luck.He did a surname search found that most Dillon's of that time were either in the parish of Tibohine,County Roscommon,or right over the boarder in County Mayo,which he had no luck there trying to find them.Rose's parent's name were William and Ellen Early,no luck finding them either.So I pcked the Parish of Tibohine County Roscommon on that basis,but am not that certain.I have been very frustated not finding my family in Ireland.I would be very grateful  for the help 

Thank You

Robert Dillon