Caring for a rose tree in a container in New England can be challenging due to the region's variable weather conditions, particularly during the winter months. Here are some tips for caring for your rose tree in a container:

Watering: Container-grown roses need more frequent watering than those planted in the ground. Make sure to water your rose tree deeply, saturating the soil in the container, but do not allow it to become waterlogged.

Fertilizing: Apply a slow-release fertilizer in the spring and then again in mid-summer to keep your rose tree healthy and promote new growth.

Pruning: Prune your rose tree in the spring to encourage new growth and shape it as desired. Remove any dead or damaged branches, and cut back the remaining branches by about a third.

Winter protection: In colder climates, it's important to protect your rose tree from winter frost and wind. Move the container to a sheltered area, such as a garage or covered porch, and cover it with burlap or a frost cloth to insulate it from the cold.

Pest and disease control: Keep an eye out for common rose pests, such as aphids and spider mites, and diseases like black spot and powdery mildew. Treat any problems promptly with an appropriate pesticide or fungicide.

By following these care tips, you can help ensure that your rose tree in a container thrives in New England's variable weather conditions.

Where I live, here in Northern Colorado, tree roses are pretty much considered annuals as they do not survive the winters here. Part of that is because they are "built" rosebushes and are not natural or typically grafted rosebushes. Here is a link to an article I wrote on Tree Roses that may help you understand more about them: https://www.gardeningknowhow.com/ornamental/flowers/roses/learn-more-about-tree-roses.htm . Also contacting a local Rose Society and asking them how to care for tree roses in your area is a very good thing to do. Here is a link to the New England Rose Society website for you: http://www.rosepetals.org/ .