Remove shell from shrimp (if necessary) and lay on a few folded paper towels. Roll up and gently press down to remove as much moisture as possible. Put into a bowl.
Preheat oven to 400F.
Pour 2 tbsp of olive oil on shrimp, toss to coat. Season raw shrimp with taco seasoning and garlic salt, toss to coat and put bowl in the fridge.
Rinse potatoes and dry with paper towels. Cut into large bite size pieces, add into a bowl. Add remaining olive oil, toss to coat. Sprinkle on remaining seasonings, toss to coat.
Pour seasoned potatoes on to sheet pan in one layer pushed to one side of the pan. Bake for 25 minutes.
Remove pan, pour on seasoned shrimp, spread out on other side of pan in a single layer. Bake for 8 minutes or until potatoes are fork tender and shrimp is pink and no longer opaque inside. Serve immediately for best results.