No, they do not taste just like potatoes, no they don't have a perfect potato texture, but they are sure good. When you pan fry or oven roast radishes they lose that bite. The flavor becomes very mild. Much the same as grilled onions don't taste like fresh onions.
If you can not have potatoes I think this is a fabulous alternative. This is a great side dish and we just love it. The next day I have to say the radishes are very soft. Just to keep in mind, in my opinion its better fresh. Although that sure did not stop us from throwing it back into a pan and adding diced sausage to it for breakfast this morning.
1 large onion
6 slices of high quality thick cut bacon
2 tsp italian seasoning
a drizzle of avocado or coconut oil for pan frying
salt and pepper to taste (if you have reintroduced)