Hello Starr –
As a primer, I’m going to recommend you take a look at our Rose Gardening Guru page. It’s chock-full of all kinds of rose growing information and I think it will help.
https://www.planetnatural.com/rose-gardening-guru/
As for caring for roses during the winter months, keep in mind that they really aren’t big fans of cold. Temps in the range of 60-70˚F are best. Depending on where you’re located your greenhouse should provide enough protection to keep them healthy and happy during colder weather. Is it heated? If not, check out our page on heating greenhouses here https://www.planetnatural.com/greenhouse-heating/. Also, make sure that your pots are big enough when you plant. A 10-15 gallon pot should be big enough for any long-stemmed variety. Inspect frequently for pests and water plants from below to prevent many fungal diseases from showing up.
Hope this helps!