In a small bowl, combine all ingredients for your vinaigrette if you're making it. Whisk with a fork until combined; set aside.
In a small bowl, combine all ingredients for your spicy peanut sauce from the peanut butter to the lime juice. Mix thoroughly with a fork until well blended. Garnish with roughly chopped peanuts; set aside.
Julienne your cucumbers, carrots, and radishes; thinly slice your scallion. Place these ingredients in a bowl, drizzle with vinaigrette, and garnish with black sesame seeds. Toss to evenly coat, and set aside.
Finally, prepare your rice noodles as per the packaged instructions. These normally don't take long to cook — so stand by and be ready to strain them and run them under cook water. Once rinsed, gently pat them with a paper towel (or shake them really well in the strainer to rid of any excess water), and portion into segments. You'll want about 0.5 oz per roll, but don't stress over exact numbers — just eyeball it!
Prepare a wide and shallow dish by filling it with lukewarm water; pie plates work perfectly for this!
One at a time, take a sheet of rice paper and submerge it into the water for about 5-10 seconds. (Double check the instructions on the package as dipping times may vary. You don't want to submerge it for too long or the paper will become sticky and unmanageable.)
Bring the paper to a flat work surface. The paper may still seem a bit stiff, but by the time you place your filling, it will have softened up. The first few rolls might be trial and error, but that's all right — packages of rice paper come with plenty, so if you have to start a roll over, go for it!
Place noodles and vegetable filling on the bottom third of the rice paper leaving 1” to 2” on the left and right. Garnish with basil and sprouts.
Wrap like a burrito by taking the edge closest to you and pulling it over the filling, almost tucking it in beneath it. (See notes.)
Roll forward halfway, then tuck in the left and right ends. Roll forward again until you're left with a nice, clean, and sealed roll!
Serve immediately with spicy peanut dipping sauce.
(Please note that summer rolls don't refrigerate well as they become rubbery, so don't make these bad boys in advance; you want to eat them fresh!)