Coat Tri-tip in olive oil so there is a coating.
Sprinkle Kosher salt, rosemary and pepper on the Tri-tip to taste.
Set the Traeger to smoke until it warms up, then turn it to 275-300.
Put roast on the smoker with the fat side up for 15-25 minutes. Then turn smoker to smoke setting, opening the cover for a few minutes allowing the grill to cool down.
Cook meat on smoke for about 3 hours. Then wrap the meat in foil for an additional 2 hours. Temp of meat should be 150 degrees for proper cooking.
Once removed from grill wait 5 minutes before slicing to allow juices to redistribute across the meat.
Tri Tip has two grain patterns. Find the line where the direction changes, cut the meat into two pieces, then cut each piece at an angle into this slices against their grain.