My folks have a couple of Golden Ninebarks in their hedge along the back of their house and I have taken cuttings and stuck them into the ground on the north side of their house and they have rooted. Not difficult at all to root. I've never tried to germinate seeds.
Good luck,
Mike

fledgeling, according to Druse, Making More Plants - physocarpus propagation is most often done with soft, green, or semi ripe cuttings.

Seed sowing for Eastern Ninebark suggestion (Clothiers)- sow 3 months (moist) @ 39ºF, move to 70ºF for germ.

If you have the seeds, you might try stratifying as for Eastern, then bringing to warm and see what sprouts. You won't know unless you try :) I find nothing in any of my reference books for sowing seeds of ribesifolius specifically