I don't know what
zone you are in Sandy so I can't tell you when to prune, but
roses are hardier than people think (my father was an expert, but that is 30 years ago). He used to prune in February in
zone 8b so I reckon that unless you are in Alaska you will be ok.
Re-rooting cuttings is another matter. Most
roses are grafted onto very hardy root stock, not just grown from cuttings. There are so many diseases that attack
roses that they have little chance of survival.
Me. I'm a nutter, so if I had loads of little bits of
rose twigs lying around, (that is If I wanted to follow in my dad's footsteps and grow
roses, and I don't) I would buy a small tub of hormone rooting powder, bang the end of the twig to splinter it, twiddle them in the powder, stick them in water, and those that rooted I would
plant and say a lot of prayers. I would also look after it like a baby. A few may survive. Gardening is as much art as science (well nearly).
oops!