Don't plant them deeper. Use bolders or large rocks up higher or above the roses,to help defuse water or slides
from washing your plants away. Bonne chance, ton ami T

How large are the plants? I always bury the complete crown of own root plants. Because of my conditions, I want mega-roots and don't like the single-cane-out-of-the-ground look. I also want a large rooted base for my plants because of high winds. I have never seen harm to an own root by planting deep. In fact, I've saved some small plants suffering from rather serious cane disease by burying the roses almost up to the tips of their canes, essentially turning them back into big cuttings and cutting off the air exposure the pathogen apparently needed.

Roses, unlike other woody plants, don't seem to mind being planted deep. I don't know how beneficial it would be with own-root roses, but it sure won't hurt them.

They might sulk for awhile but eventually the cane portions below ground will root and create a healthier plant that can sustain more above ground growth.

Thank you all! Exactly what I was hoping! I feel much more confident and am now looking forward to my effort. I was hoping, if planted deep, it would encourage more rooting and stronger anchors for the steep hill, wind and erosion issues, plus retain more moisture for a better chance to adapt and establiship for permenance. I'm planting Devon?, Treasure Trove, White Banksias, Cl Cecile Breuner, Mermaid, SDM, Blushing Lucy, Darlow's Enigmas, Westerland and more I can not think of at this moment. I'm grateful for your combined wisdom and encouragement. I'm off to begin now, yesterdays good rain has prep'ed the hill and more rain expected sounds helpful. I don't expect Missy's or Pam's breathtaking results but hope for the best I can create in my location. Thanks again .....