Pine straw is an ideal mulch for roses. Other good mulches are peat moss, rotted sawdust, wood chips, and rotted cotton burs. If mulch tends to pack, a thin layer of mulch is needed. But don't take it off and apply new mulch, unless you've slipped up on spraying and let blackspot leaves drop. Just keep adding mulch as it rots and settles down. Mulching prevents evaporation, thereby requiring less watering. It prevents freezing and thawing in winter that could damage plants beyond recall and helps prevent weed growth. Mulching also adds organic matter. If mulch packs, break it gently so water can soak in. Tender feeder roots are on the soil surface, so do not cultivate. A good mulch will do the job.
When weeds come through, it will be easy to pull them. How often to water? Pull back the mulch. Test an inch or two into soil for moisture. If soil is dry, then water. (Soak beds every seven to10 days unless it rains.) It's best to avoid watering leaves when watering roses; always water the base. Water throws blackspot and mildew spores all over the bed. A healthy rose bed is trouble to establish and maintain, but surely worth the trouble!