With 30 years of experience in the landscape industry working in the Portland, Oregon area, here are a few pros, cons and tips I’ve learned about planting in the winter:
1. Marginal Plants

As a general rule, winter is a good time to plant. However, if the plant is marginal for our area (sometimes dies from a hard freeze), you may want to wait until spring. Most of these varieties of plants are stored in a protected area at nurseries or are grown out of state. If they are planted during the winter, their roots have not established substantially. This makes them more susceptible to damage.
2. Limited Availability
Certain plants are simply not available at the nurseries during the winter; but historically, most plants are.
3. Nature Helps Water

Homeowners without sprinkler systems will greatly benefit from the wet, cool weather in the Portland area which keeps plants watered and moist naturally.
4. Don’t Plants Hate Being Planted in the Cold?

If you think about it, in the winter, plants are usually sitting in a nursery yard exposed to the elements in plastic containers. They are fine with this, but if they’re planted in the ground, their root zone will have the added insulation of the surrounding soil. Plus, they can begin setting roots during warmer winter days. This will give them the best chance at coming out strong in the spring.
5. Bare Spots in Beds
Many plants naturally die back in the winter. Because of this, it may look like a 1-gallon container of just dirt is going in the ground. This makes it not as rewarding for clients to see their new landscape – because areas of their beds appear bare. But, of course, in the spring, the new plants will pop up in all their glory.
6. Transplanting

Plants are dormant in the winter, so it’s a great time to do it. Transplanting season begins after the first hard freeze. It takes a hard freeze to trigger plants into dormancy. Since they are dormant and resting, it’s the safest time to transplant them. For many plants, it’s the only safe time to transplant them.
Can you replace an older rose garden, 15 tp 20 bushes now about 10 years old with an all new set of bushes at this time and have roses in the spring and summer?
Thank you for your question! Yes, winter is a fine time to plant roses. However, sometimes they may not be available a the nurseries, so you’ll need to check around. Here’s a good article providing more detail about planting roses in the winter. https://garden.org/ideas/view/chelle/1685/Winter-Planting-Roses/