I hesitate to reply, because I don't have a hard connection, but I do have a tenuous Carroll connection in Allegheny Co and thought I'd pass this along.
My 3g grandmother was Ellen CARROLL, b. abt. 1821 in IRE, married Patrick (Mc)Cluskey in Ireland, moved to Durham Co. England. Their daughter, Margaret, b. IRE 1849 married Michael O'Grady in Durham. They emigrated to the US -- South Fayette, McDonald PA/Allegheny Co abt. 1869.
Residing next door in the 1880 census was the following family. I don't know if they were related, but have often wondered:
Barney Carrol, age 35, b. Ireland Margaret b. Ireland Bridget (b. Scotland)15 Catherine 10 b. PA Patrick 8 b. PA Margaret 5 b. PA Ann 2 b. PA Elizabeth 10 months b. PA