It looks like your project is coming along very nicely! I enjoy seeing it at this stage.
I lived in Rockport for four months one spring. I was doing computer programming work at the time and my only connection to nature was to take walks and drives to see what was growing in peoples' gardens from the sidewalks and roads. I found that part of the coast to be an almost magical spot in spring.
My SWAG is that with adequate mulching (two inches or so?) the roses will be fine. I'm pretty sure Knockouts and wichurana ramblers will be cold hardy to at least zone 5, so they should not freeze to death. I think the greatest fear might be desiccation, although it seems to me that humid sea-breezes during the winter would actually tend to keep that from happening. If weather is exceptionally dry in March and April when the roses start to set leaves, check to make sure that the soil is still moist. Maybe give them a little Mills Magic or some other organic fertilizer at about the same time. Again, you planted some of the tougher and more vigorous rose cultivars to be found; not growing could prove the least of your worries.
