I am transplanting a very mature rose brush from a wet west coast climate (Vancouver BC) to an arid semi desert climate (Oliver BC). It started to snow when I moved. Right now I have the rose brush in a plastic bucket with some soil and water in the house. What should I do now?
You need to re-acclimate it to the outdoors and plant it. It is a difficult time to transplant since nourishment for the rose over winter is stored in the roots. No doubt some were cut in the transplant process but it is worth a try to keep it, of course. Improve the soil with compost (and peat if the soil is sandy) and settle it in. Water well and mulch 4-6 inches over the roots and crown. Remember to remove the crown mulch in early spring and decrease the root mulch to 2-3 inches. For an extra degree of protection, consider caging the rose with chicken wire and filling the cage with chopped leaves or straw. Unless you have a shredder, don't use maple leaves as they tend to mat down and inhibit air flow. Winter is a lovely time to read catalogues from the major rose producers. Catalogues will help you find a rose that will thrive in your new environment.