Now that our nights are regularly in the low 30's, with lower in sight over the next week, could I safely cut back those giants? Or would I still be at risk of triggering new growth?

Not sure if the new growth is purely temperature dependent, or also affected by daylight....

Am I reading right that your point is you think the roses may have gone dormant, and that a bit of pruning is not likely to trigger tender new growth? It sounds logical, but I speak from a weak position here. My earliest gardening years were spent in a cold winter climate (zone 6a) but I didn't know much at the time, and I've forgotten much of what I did know back then.

I can reassure you that roses are day neutral. Day length does not affect their flowering or their dormancy as it does with some plants (called photoperiodism).

If you do prune and move one of the roses now before the ground freezes solid, there is always the problem that if the plant is dormant, you aren't going to get much root growth in the new location until spring. I can see some potential problems with that as well.

However sometimes the need to move a plant is so compelling that the risk is worth it. Please let us know what you decide, and how it turns out.

Rosefolly

For modern roses like HTs, flories and shrubs I wouldn't prune until spring unless the canes will whip in high winds all winter. Even then I would only cut them back a little and/or stake them instead. Roses store energy in the canes for next spring and pruning them reduces their resources.

Some OGRs are very sensitive to pruning. They need a big build up of twiggy growth to be happy. Once bloomers will not flower next spring if heavily pruned back now OR in the spring because they set their buds on old wood. If you cut it off you cut off your bloom. They should always be pruned back immediately after they finish their bloom cycle so new growth will have time to mature so it will bloom for you next season.

Types - The two old ones are rugosa hybrids Therese Bugnet, four years in current location, oldest one was new in 1988, second was a sucker from early 90's. They love the new location and have turned into blooming monsters. But they are obscuring the sight lines for good sized bushes that are UPHILL behind them - plus throwing off the scale of the whole garden and nearly blocking one of the stone paths. They have pruned in the spring every year, but this year was just incredible for new canes, which are as long as the old ones, and not as sturdy, so I do fear winter wind damage.

Newest one which I want to move is only three years old, gallica Allegra, which has to go against the deck trellis for support, I want to see how big it will get since it has overwhelmed the spot its in after just two years. It is just too tall and spreading too far. I can support the height and width with ties to the trellis.

Current plans - cutting all three back before winter storms, not right now, but making the Allegra move next spring.

If you cut Allegra back now or in the spring you'll lose next year's bloom. If you can move it next spring without pruning it try to do so. Immediately after it finishes blooming next season you can cut it way back if you wish. It'll just grow back with a vengeance though, lol.