I’ve tried roasting radishes. You have to spice them well, and roast them long enough for the moisture to cook out. Nothing equals the pleasure of potatoes, but they can be an acceptable substitute, if you cook them long enough. But no, microwaving won’t work.
I’ve had very good yuca fries, but I think they were coated in something to make them crisper, and they are extremely high in carbs. I’d say to test your blood sugar one and two hours after eating them, to find out if they mess yours up or not. I had the same kind of addictive reaction after eating them that I get after eating potatoes, so from that I know that I need to stay away from them.
Roasted Brussels sprouts have filled that spot that potatos used to fill in my plate. Halve, toss with olive oil, salt and pepper and absolutely blast them in the oven. I like them just this side of burned, done right you get a crispy exterior and tender inside.
If you like tots as well as fries, I have seen a lot of broccoli and cauliflower “tots” but I am not sure if there is breading involved. My wife used to have me buy this vegetable, I can’t remember the name (Mexican something was the slang I believe) that was potato like but had the consistency to me that seemed sort of in between a potato and a carrot and she used it in some recipes.
I’m happy that I’m never giving up potatoes, especially not sweet potatoes if I have to go that route.