Hi tobbria. In my opinion a day trip is definitely sufficient for Ronda, although quite a few people will say that they like the quiet of the night when the tourists have left.
Granada is only an hour or so from the city of Malaga, but I would advise that you make an overnight stay, as you don't want to rush around the Alhambra.
The snow in Sierra Nevada should start falling at any time now and the view of those mountains from the Alhambra is stunning. The
ski resort is only 30 something kilometres from the city and worth a visit too if that floats your boat and you can hire the equipment up there if you want to whizz up and down the slopes.
If you are visiting those places, dress correctly because Ronda can be as cold as Granada in the winter. On a couple of occasions last year the road from San Pedro de Alcantara on the coast to Ronda was closed because of snow.