I'm in zone 7. Our daytime temps are between 40 and 60 with nights in the 20s and 30s. I put several rose cuttings in my hoophouse a few weeks ago. They made it through several nights of 18 degrees.

As for the hydrangea, I wouldn't move it out until spring. I think they're too tender.

Hello,

Maybe I can offer you another choice. If you will scroll down through the link below to the pictures posted by Hartwood, that is what my rooting pots look like, except that I sit mine on the patio outside in the shade during the summer. I just don't have a space to start them or bring them inside for the winter, so I bed them - with pots and domes and a little extra mulch built up on the sides of the domes - on the south side of the house. Temps here have been as low as 10F several times, and below 20F lots of nights, and my rose cuttings are still doing well. I don't have to tend them, they get watered when the domes don't have condensation on the inside. Plus no blackspot.

Best wishes,
Gary

Here is a link that might be useful: dome rooting