Kia Ora Jason,
My tree has a William Roulston ?1815? m unknown. with two sons: James and David (1833-1916).
David married Elizabeth Elliott (1838-1887). Their fammily William (1860-1923), Jane (1862), Martha (1863-1961), Margaret (1864), James & George ( 1867 ), David (1871), John (1873-1930), Dorcas (1875-1956) and Thomas (1881-1918).
Unfortunately I dont have the townlands these Roulstons were from. My Bates family appear to have been originally from Garrison Hill although I do note that there were Bates' registered as Flax growers in Raphoe from 1776. I haven't got connections to the 1770s families.
The family churches appear to be Donghamore and Carnowen.