Is there a change in how to cook it due to the size?
From this site, here is Anne Seranne's "genius" recipe for oven-roasted.
Be sure to scroll down to the bottom of the page to read though the comments, which may be useful.
If you go over to SeriousEats.com and search on beef rib roast, you will also see some recipes for grilling the roast.
I second SeriousEats.com