How do I convert a grilling recipe to an oven/ broiling recipe?
Since you mentioned a butt in your question, I'll start there. The way to get close to the crispy sear and smokey flavor you get from grilling is, surprisingly, to cook the butt at a very low temp (~200-225 F) until the internal temp. gets to about 135 F. 

Before putting the roast in the oven, you want to massage a generous amount of olive oil all over the meat and season it to suit your tastes.

When the internal temp gets to ~135 F (count on 3-6 hours depending on the weight), remove the roast from the oven and tent foil over it. Heat your oven to its hottest temp (~500 F). When the oven is fully heated, uncover the butt and put it back in the oven until the internal temp reaches between 145 F (about medium) to 165 F (well done).

This method will give your meat a nice crunchy sear on the outside, while leaving it juicy and flavorful inside. The high temp at the end will also create some smoke and add to that grilled flavor.