You can dehydrate the sweet potatoes. I have only used yams for my joggers paradise juice. There is a book for raw vegans and I just cannot remember the name and it mentioned steaming the vegetables. If you want to do that then that is your choice but because water has to be at a high temperature to boil to lightly steam your potatoes or yam it would be controversial to call it raw.
Renee Underkoffler’s book Living Cuisine has many recipes with steamed vegetables on it,and Gary Null (www.garynull.com) always said that lightly steamed vegetables such as cauliflower,brocolli,are much better for you because the lightly steam opens up the enzimes and makes them easy to digest.