Prepare all vegetables by washing and chopping as prescribed.
Combine sauce ingredients in a measuring cup or bowl.
Heat avocado oil in a large skillet or wok over medium heat. Add carrots and onion first and let cook for a few minutes. Then add the rest of the filling vegetables. Stir often and cook until soft. Add half of the sauce and cook for the last minute. This whole process should take about 7 minutes.
While the vegetables are cooking, soak vermicelli in a bowl of boiling water for a few minutes until soft. Be sure to watch them so they don't over-soak and become gummy. Drain and rinse with cool water.
Transfer the vegetable mixture and the vermicelli to a large sheet pan. Place in the fridge or freezer to cool for about 5-10 minutes.
Once ready, take the filling mixture out and set up your workspace. You will want a large bowl of lukewarm water, a plate, a kitchen towel laid on the counter, and the sheet pan and other toppings to be handy.
Take 1 rice paper sheet and fully submerge in the large bowl. Continually flip the sheet over for about 30 seconds. The sheet is ready when it has slightly softened, but is still a bit firm.
Place the rice paper on the towel. Place a scoop of filling in the lower centre of the sheet. Add any fresh fillings such as cilantro, chilli pepper, or mango.
To roll, fold the left and right sides in as tight as you can. Then, take the bottom and wrap it around the filling, and keep rolling tightly until complete.
Repeat the rolling until you have enough rolls. If you are not going to immediately eat the summer rolls, you can store the filling in the fridge in an airtight container for 1 day, and roll right before serving. Pre-rolled rolls will turn gummy and not keep very well.
Dip the summer rolls into the reserved sauce and enjoy! You've made a fresh and healthy dish that is gluten-free, dairy-free, and vegan.