Hmmm...
My recommendation regarding the Lloyds of Croghan was based on:
(a) "I believe there is/was a memorial inscription to our family at Elphin cathedral". The first Lloyd to settle in the area,
Owen Lloyd of Croghan (1631-1664), was buried in the Cathedral Church of Elphin.
It may be safe to presume any Lloyds in the Elphin-Croghan area originate from this man in some way or another (until proven otherwise). If not direct descendants, then English cousins brought in to support their activity in the area.
(b) "My ancestors lived in "Smith Hill house"
The Lloyds of Smith Hill were a branch of the Lloyds of Croghan. (Click on this link to see the record on the Landed Estates database).
Smithhill House was in the demesne of The Palace at Elphin. It was the residence of the Reverend Oliver Jones, grandfather of Oliver Goldsmith, in the early 18th century. It was the home of Robert Jones Lloyd in the late 18th and early 19th century. He was a member of the Grand Panel of county Roscommon in 1828. He was married to Susannah Devenish of Rush Hill and died in 1832. He appears to have been a middleman in county Leitrim.
In 1837, Smithhill House then became the seat of the Reverend John Lloyd, rector of Aughrim, (a kinsman of Oliver Goldsmith). On 28 Nov 1847, Lloyd was famously murdered by his tenant Owen Beirne of Caldra.
One Rev. John Lloyd, who ran a school denounced by another priest as a “factory where numbers of famine Protestants are manufactured,” was also murdered, a month after Major Mahon, though whether this was for being an evicting landlord or for proselytizing is unclear. (Famine's Villains NY TIMES)
Clearly, this is why your family ran out of the place! If you run an in-depth search on the British Newspaper Archive you will find plenty of coverage of this 'Outrage in Elphin'. Beirne was hanged the very next day.
Smith Hill house was unoccupied at the time of Griffith's Valuation (1857) when it was valued at £8 and held by Robert Lynch. In the 1870s Robert Jones Lloyd of Twickenham, London, owned 300 acres in county Roscommon and 892 acres in county Leitrim.
Hope this helps.
So, with that in mind, you can start here...
Owen Lloyd Esq. 1631 and here Croghan & the seat of Guy Lloyd Esq.
and dig around the Landed Estates database to see if you are, in fact, any way connected to the Lloyds of Rockville who also originate from the Lloyds of Croghan House.
You might also follow the Goldsmith trail for clues. The Ordnance Survey Field Name Books record that Goldsmith's father was born at Ardnagowna. See also Ballyoughter House (where Oliver Goldsmith's father was also supposedly born and where Oliver Goldsmith himself spent part of his childhood) which is also in the parish of Elphin.
As for Roscommon Infirmary...
You are probably in luck, as the Old Infirmary is the Roscommon County Library. Why not get in contact with them to see what records they hold on Robert Jones Lloyd. Also, check out http://www.workhouses.org.uk/Roscommon/
Best of luck!