Thomas Carroll enigma!

I have a brick wall and I need some new directions to go.  The problem is the name of the person is "Thomas Carroll".  I know when he was born only from his tombstone and death certificate.  The first census in which he could definitely be identified was in Fairfax Station, VA - 1860.  I have a lot of other information, but here's the problem.

From the beginning of the Irish famine and soon after, so many "Thomas Carroll"s came over on ships.  Some of them even have the same birthyear of my Thomas Carroll, 7 Jul 1831.  His death cert says he was born in County Tipperary and his father was "Thomas Carroll", no mother's name given.  In Tipperary, Thomas Carroll is a very common name.  How can I ever discover when he came to the US, got married (which he did), or who his family was?

I am stumped.  Any suggestions would be helpful.  I can follow his life from the 1860 Federal Census, but there is nothing before.  Help!!