In a small bowl, mix the wasabi with the tamari and the oil; add the scallions and tuna and mash with a fork to combine.
Heat a large skillet over high heat and blister the tortilla for about 30 seconds on each side to soften and toast. Transfer the tortilla to the countertop and let cool for about 1 minute.
Top the tortilla with an even layer of the spinach and then the tuna salad. Fold 2 sides of the tortilla over the tuna and tightly roll up the tortilla to enclose the salad. Cut into 1-inch-thick slices to make the pinwheels.