Using a melon ball scoop, cut into each tomato at the stem end and carefully remove all of the seeds and pulp. Cut a leveling slice at the bottom of each tomato so the tomato sits level on a plate.
Place 1 leaf of the red leaf lettuce flat on a work surface and place 1 leaf of the radicchio directly on top. Place 1 each of all of the remaining ingredients (except use 4 to 5 mushrooms per serving) on top and roll up tightly. Repeat with remaining ingredients.
Using scissors, snip off the bottom of each "bouquet" even with the scallion and place in the center of each tomato. Open slightly to display all of the greens.
Spoon 2 tablespoons dressing in the center of each salad plate and place 1 tomato in the center. Arrange 2 cucumber rounds in the dressing and serve immediately.