As above Kippford or Gorsebank are both great. You can ride straight onto the Dalbeattie trails from Gorsebank and the ‘wigwams’ are great.
Also have a look at Coastal Kippford Holiday park[/url], very nice lodges for hire, 30 seconds ride to the trails and a nice walk or ride through the woods down to the Anchor in Kippford.
Don’t know what Roughfirth House is like as a B&B but it does look a bit tired and I’ve not seen many cars parked outside and I’m down there a lot.
Rosemount Guesthouse in Kippford is also really nice. The anchor hotel has rooms but they’re also bit tired, clean enough but in need of some TLC.