I love researching weekends away and I don't want to get off my couch so I did some googling for you. I based it on weekend rates.
Leitrim:
http://www.thelandmarkhotel.com/
(Offer 2B&B & 1 Dinner for €135pp - weekend rate - no leisure centre/spa)
http://www.loughrynn.ie
(Offer
1B&B & 1 Dinner for €105pp - weekend rate, to add another night is 80pp approx, difficult to price on their website - there is a leisure centre/spa)
Donegal:
Tripadvisor's top two hotels are:
1)
http://www.harveyspoint.com
(Offer 2B&B & 1 Dinner starting at €169pp depending on your chosen dates - there is a leisure centre/spa)
2)
(Offer 2B&B & 1 Dinner starting at €225pp depending on your chosen dates - there is a leisure centre/spa)
Roscommon:
Tripadvisor's top two hotels are:
1)
http://www.gleesonstownhouse.com
(Offer 2B&B & 1 Dinner for €125pp - no dates specified - no leisure centre, appears to be a great place if you are a food fan)
2)
http://www.kilronancastle.ie/
(Offer 2B&B & 1 Dinner for €169pp - weekend rate - there is a leisure centre/spa)