To make the crispy tofu, cut the tofu into 5-inch long strips that are roughly 3/4 inch thick and wide. Pat them dry with paper towels. Heat the canola oil over medium high heat and add the tofu strips in an even layer in the hot oil, working in batches as necessary so you don't crowd them in the pan. Fry until golden and crispy on each side, turning as needed, about 4 to 7 minutes per side. Remove and set on a plate lined with paper towels. Allow to cool to room temperature.
Before you being assembling the rolls, make sure all of the ingredients are ready and placed around a clean work surface. Fill a large bowl with warm water. Submerge one of the sheets of rice paper in the water until it is soft and pliable, about 10 to 20 seconds. Place the rice paper flat on the working surface and place 3 of the large radish slices down the center, leaving a couple inches of empty space at each end. Place a piece of the crispy tofu over the radishes, followed by a small handful of the arugula, two of the green onion stem pieces, and a pinch of the cilantro.
Fold the left side of the wrapper over the filling, then fold the right side over the filling and press down gently to secure. Hold the whole wrap firmly in place and fold the top and bottom flaps in and press gently to seal. Repeat with the remaining ingredients.
To store, you can wrap the rolls in plastic wrap and keep them in the refrigerator for up to 3 days.
Whisk together all of the ingredients in a medium bowl until smooth.