How heavy is the roast?
Cooking it at a steady 325 or 350, going blast and slow, or slow and blast will give you similar results. Any method which involves mostly slow cooking will be more forgiving in terms of getting the final temperature right in the sense that you'll either have a larger time window (blast and slow), or will be right on top of it at the end (slow and blast), but none are inherently superior.
The differences in the methods, such as they are, are more pronounced with smaller pieces of rib roast -- such as yours -- but not enough to fret over. It's really all about the quality of the meat itself. Don't do anything to screw it up, and you'll be fine.
I can and do get great "bark" (aka "crust") on standing rib cooked in a smoker at 250F (with a water pan, yet), so trust me. Low temperatures aren't that much of an problem when it comes to the roast's outside. If you want super dark, you can always paint it with Kitchen Bouquet before seasoning.
Unless you're cooking the roast at a very high temperature, the evenly cooked appearance Koukouvagia talks about comes more from the rest than cooking temperature strategies. The fat cap (if you have one), "tail" (the super tender, fatty meat wrapped around the top of the eye), and bones will all protect the eye from overcooking and getting dark -- as long as you pull at a reasonable temperature. An internal of 125 with a 20 minute rest is standard. For a 2 bone roast, 15 minutes might be enough... or not.
FYI, you want the tail to both be more cooked and appear darker than the eye. It's a very fatty piece of meat, delicious when well cooked, but not palatable when underdone.
Finishing with a torch is appropriate for a steak cooked sous-vide, or otherwise done very, very low; but inappropriate for what you're doing. I love my torch and am not shy about using it; so this is another trust me.