Ugh! I've been dealing with the same thing. Planting in shady-acidic soil can be difficult at best. You may want to consider building some raised beds where you can control the pH and quality of your garden soil. If, not consider acid loving plants, like azaleas, rhododendrons, blueberries, and holly. Roses like a slightly acidic soil and should do well there too! Just make sure they get enough sun.
I can't tell what's eating your rose plants from your description, but once you ID the little buggers, they shouldn't be too difficult to keep under control. Here are a couple of other suggestions:
• Add lime to adjust your soil pH
• Add plenty of compost – it will build your soil and tends to neutralize pH
• Trim the lower branches of your fir trees to allow more light through
Good luck and let me know how it turns out!