You could put a heating cable in the soil under the plants, which would warm the root zone as well as radiating some heat to warm the foliage. Twining it around the plants above ground probably wouldn't do much good. Upright rosemaries can't be "trained" to have a different habit. As your rosemary grows, you will wind up with an enlarged prostate.

oh, prostRate rosemary. I thought maybe this was another iVillage marketing scheme.

actually I read that BOTH spellings were correct (prostate, prostrate) since the herb has also been used medicinally for prostate problems!

This is a classic example of folk etymology. Where an unfamiliar word is replaced by a familiar one which then starts to be accepted. The plant is Rosmarinus officinalis 'Prostratus' coming from Latin and meaning it lies flat along the ground. Nothing to do with prostates at all. It would be unkind to let somone go on saying 'prostate' rosemary without alerting them. They would never know why people were sniggering. Just as when a friend of the family insisted there were bits of octopus testicle in the fish soup.

As it is the OP clearly meant 'prostrate' as the typo only occurs in the subject line.

Here is a link that might be useful: Folk Etymology

Hee hee! Octopus testicles! Thanks for the giggle, flora!

FataMorgana