Dust the shrimp with the Creole seasoning. Heat the olive oil in the skillet over medium heat and cook the shrimp until completely pink and firm--about three minutes. Remove and allow to cool.
Tear the romaine into bite-size pieces. Place in a large bowl. Add pasta, shrimp, and roasted onion vinaigrette, and toss until combine. Arrange on serving plates, garnished with tomato wedges and cucumber slices.
For the roasted onion vinaigrette, in an ovenproof container with a lid, combine the onion with 2 Tbs. olive oil and the Creole seasoning. Cover and bake in a preheated 225 degree oven for two hours. Cool to room temperature.
Add remaining olive oil, vinegar, salt, and pepper to taste. Stir well. This dressing can be stored, refrigerated and covered, for two weeks.