Keenan family

I have two places of origin for my Keenan ancestors. The same person supplied his place of birth as: -

1) Rosslea, Co. Monaghan and

2) Scotstown, Co. Monaghan.

I therefore suspect the family farmed somewhere in between? Did borders between Co. Fermangh and Co. Monaghan change in the 19th Century. My family came to Scotland in the 1840s so I suspect I won't get back any further but I'd like, if possible, to work out where (area wise) the family lived. I have found the marriage of my 3 times great grandfather's brother in the RC church in Tydavnet i.e. Francis Keenan to Sarah Clark. Francis and family also came to Scotland.

Am I right in understanding this is Clones Parish? Any advice appreciated.