Now is a fine time, any time in between the end of June, and the first heavy snow. George Mander and Cheryl Netter have written articles about how it's done; you can also search for threads on this forum by object16 - I know object personally and he's quite accomplished at growing cuttings, and he learned from George and Cheryl. Your medium doesn't need to be sterile, like some books say - you can use pro-mix, peat based potting mix, shredded composted bark, shredded composted christmas trees, or other exotic items. Object16 (Paul M.) likes to mix in 25 - 30% sand, moisten the medium, he uses 3.5" or 4" peat pots, and he puts them in standard trays, covered with a tall "Humididome", which is a platic cover with vents, crack open the vent a little, put it about 6" from a twin tube shoplight, and keep it between 70-80 degrees (use a thermometer to be sure, like a cheap one from waly-mart with a probe at the end of a wire).
He cuts the cutting straight across, right below a bud, and breaks off any prickles that would be below the ground level. this breaking off of prickles is instead of wounding, he doesn't find wounding with a knife actually accomplishes anything other than serve as a portal for disease entry, but other people use a LIGHT scrape with a pin or the side of a razor, or razor sharp knife like a stanley knife or something. Bury one of two buds, and have one or two leaves exposed, but trim any excess leaf size so it can fit in the humididome. Usually within 4 - 6 weeks you have strong new growth, indicating roots - put them in larger pots and grow on over winter under lights. By next spring you'll have nice sizeable bushes, and by the end of next year, you'll have something really impressive. You can search for threads started by object16 for some more of his tips, and I've learned a lot from reading them. But like I said, he learned from reading articles by George and Cheryl;
the main difference is that he cuts STRAIGHT across below a node instead of an angled cut, and he DOES NOT WOUND, except by breaking off prickles, he uses ROOTING GEL, instead of powder, and uses fairly short cuttings compared to what other people use - do realize though, that roses can even be propagated by even a leaf bud cutting - just one bud with its leaf, but you'll get more cuttings root with a more generous sized cutting - with in between 2 to 4 total buds.

Thanks so much for the great explanation. Very helpful. I appreciate it!