Grill tri tip and let stand.
While tri tip is resting, lightly brush cut sides of rolls with prepared dressing. Place rolls (cut side down) under oven broiler for 1 to 2 minutes or until golden brown. Turn rolls; sprinkle with cheese. Broil 1 to 2 more minutes or until cheese just begins to melt.
While bread is heating, combine spinach, tomato and basil; toss. Remove rolls from oven and place an equal amount of the mixture on each roll half. Carve heated tri tip across the grain into thin (1/4") slices; arrange beef on spinach mixture. Serve open face. Combine with a deli pasta salad and you have dinner for four adults in less than 20 minutes!