Preheat smoker to 225°. Place tri tip roast on a cutting board, or a tray covered in foil.  Drizzle a little oil over the roast (about 2-3 teaspoons) and rub to coat all sides.  Drizzle 2-3 teaspoons oil over your roast and rub on all sides.

Sprinkle steak seasoning (or kosher salt and pepper) on all surfaces of roast, turning to cover ends and sides as well.  

Place roast on smoker and close lid.  Cook until internal temperature on the thickest part of meat registers between 130-135 for best results (medium rare).  This is generally about 30 minutes per pound, but make sure to use a digital thermometer where you can constantly monitor your temperature without opening the smoker too much!

When roast is getting close to being done, heat a cast iron (or other heavy-bottomed pan) to high heat.  This can be done on a bbq grill or indoors. 

When roast comes to temperature, remove from smoker.  Place about 2 tablespoons butter in the hot cast iron pan to melt.  Place the roast in the pan and let sear for a minute or two, until a golden caramelized crust forms. (Though I prefer this skillet/butter method, you could also simply give your roast a quick sear directly on hot bbq grates).

Remove from pan and place in heavy duty foil, wrapping tightly.  Let sit for 5-10 minutes. 

Slice tri tip against the grain, taking note that the grain of the meat changes direction slightly when you get to the largest, thickest portion.

Pour remaining butter from hot pan (be careful, the handle is hot) and also the meat juices from the foil, over the sliced meat.