One more question. These Wood Roses are currently covered in rose hips. How do I collect, store, and germinate those seeds?

Division: No idea. I've not seen multple stems from the ground -- not more than 3-4, I always assumed is was multiple seeds from a single fruit.

Seeds: Last year I collected a bunch, and planted them in styroblocks, 5cm x 12cm cells, 2 and 4 seeds per cell. Germination rate is about 30% -- I'll go with 4's this year, and clip the extras.

Plant ~1/8 to 1/4" deep. I put a quarter inch of chicken grit on top as a weed reduction measure, mulch, moss inhibitor.

I'm not sure if you already know this, but if you decide to sow seeds, make sure they go through a cold period - you'll be better germination. Best way would be to sow them, cover the container (or put the pot in a ziplock) and put it outside for the winter. They should sprout on their own around when the bushes start to leaf out again.