How do I prepare roses for the winter in SW Washington?

Answer 1

Part of the answer is what sort of roses do you need to 'prepare'.

I'm guessing you're in a pretty mild USDA hardiness zone (8?) I on the other-hand am in burr-burr cold zone 5.

You should have to do very little.

Cut away any rambunctious out of control branches, and even up the whole plant. (This is supposing that the rose in question is a hybrid tea, grandiflora or floribunda) Water as normal until the plants are dormant.

In the spring, when the first indicators are showing activity (here in Michigan I wait until the Forsythia are in bloom to prune my roses, you might have the same or another shrub that indicates that 'spring is here') and then I prune. Cut away any weak, damaged or diseased branches, then remove crossing canes. Lastly reduce what is left so that all remaining canes are at least the thickness of a pencil. Fertilize in the spring.

I would give my 'eye teeth' for the gardening conditions you must endure (I hope you appreciate my jealousy).

Good luck

Answer 2

Well, according to my zone map you are in zone 7 or 8 which means you don't really have to do anything except maybe some pruning. A little straw around the base of the roses if they are young, but not necessary if the roses are mature. Zones 7 and 8 are perfect for growing roses.
http://www.bayeradvanced.com/article/how-to-prune-hybrid-tea-roses.html?source=google
Video from Expert Village on how to prune a rose:
http://homegarden.expertvillage.com/videos/deadheading-roses.htm