Peter Cleary, born 1821 - married Isabella Linsley in North-East England (Durham I believe). Evidence for him being from Kilmore is the 1881 E&W Census listing him (Peter Clarry ) as being born in Kilmoor, Ireland. And I think I've seen Rilmore somewhere too! I've seen others on Ancestry listing a James Cleary, born 1790 in County Clare as his father, but I haven't found documentary evidence of that.
There is a Kilmore in Co. Cavan. A parish and also the name of the entire diocese.
That your Peter Cleary ended up in Durham, might suggest mining - did he have such an association? There were mines in the vicinity of Co. Cavan, which might make a Cavan origin more likely if so. Downside is he would have been born before start of parish register.
There is also a Kilmore Catholic/civil parish in Co. Mayo, on the ocean.
Kilmore, Co. Wexford - A parish with fishing village and an agricultural area. Unlikely candidate for move to Durham? No sign of his baptism in parish registers.
Kilmore, Co. Clare - just a townland.
There is an association with mining, yes, when looking at the census records from the UK and US (Lackawanna County PA is known for mining, I believe), right up to my grandfather who was a coal minor in County Durham.
I'll try to get hold of the Cleary-Linsley marriage certificate.
As for the Roche side, I'm inclined to think now that the Fermoy or Macroom angle for Mary Bridget Roche is a red herring, as the mother's surname there is Daly. Although County Cork being listed as her birthplace on the 1911 census is still interesting. Looking at the Irish birthplaces of her siblings, though, they did seem to move around a bit - Lower Aughrim, Baltinglass, Rathdrum, Kiltegan. I don't know if that was normal at the time.