I need a good beef stew that uses leftover beef from standing rib roast??

shepards pie!

You probably won't want to cook the leftover rib roast for a long time like a stew as I imagine the meat may get too chewy. You can maybe cook the vegetables in beef stock and wine first, and then add the beef toward the end just to warm it up. I've done that to make pie filling with leftover rib roast before.

bet it would make a great french dip sandwich w/ au jus.

Or just warm it up a bit or eat it cold. A leftover standing rib roast doesn't seem like a great candidate for a stew.

I don't have a stew recipe for you but have you considered roast beef hash with those leftovers? A few boiled potatoes diced with the diced meat, onions and lots of black pepper make for a wonderful leftover supper!