Preheat oven to 400F.Place chopped potatoes in large bowl with rosemary, olive oil, salt, and pepper. Toss to coat. Dump potatoes on baking sheet and spread out in an even layer.Roast in oven for 45 minutes (or until tender), stirring halfway through. Remove from oven and add sliced mushrooms and walnuts. Bake for another 10-15 minutes, or until everything is browned.Meanwhile, place dressing ingredients in a blender or food processor (I used my Nutribullet) and blend until smooth.Dump kale into a large bowl. Add dressing and massage into leaves for about a minute (if using lacinato, massaging is not necessary.) Add lentils and baked potato mixture. Stir to combine and season with salt and pepper to taste.