there seems to be very few people with that exact surname in Ireland - e.g. on Griffiths Valuation (1847 to 1864 ) there are a total of 12 households in all of Ireland.
Roscommon 8
Sligo 3
Mayo 1
from Slaters directories :
1870 : Patrick Morrisroe , Ballinafad, Boyle Co. Roscommon - Grocer
1881 : Morrisroe Patrick, Ballinafad, Boyle Co. Roscommon - Publican
1894 : John Morrisroe, Charlestown, Co. Mayo - Baker
the Irish Family History Foundation website at
www.irish-roots.ie includes Counties Roscommon & Mayo. Its a subscription site - parish records transcripts cost €5, index is free to search once you register.
a search for Thomas Morrisroe between 1846 and 1854 shows one result :
Church Baptism Morrisroe Thomas 1853 Co. Roscommon
the record seems to be from the Catholic Parish of 'Tibohine-Fairymount'
There's a town named Tibohene about 7 km east of Ballaghaderreen
Shane