I have smoked a prime rib, several different times, with a coating of cajun mustard covered in freshly grated horseradish. You end up with a crust of horseradish that you can peel off and discard. The flavor of the horseradish is throughout the prime rib. I like it.
Tee and I used a there fresh horseradish to encrust a tri-tip. It, too, was great.
You just have to love horseradish.
Art