Move the rack in the oven to the lower middle position. Place the roasting pan in the oven.
Preheat oven to 425F.
Slice the greens off the turnips and radishes.
Scrub the turnips and radishes well to remove all the dirt and grit from the vegetables, and rinse the greens repeatedly until they are grit free. If you left a little bit of the stem on the radishes and turnips, make sure you clean around it well since dirt collects there. I find scraping around the stem as I wash cleans it up nicely.
Cut the turnips and radishes into wedges. Halve the small ones, and quarter or sixth the larger ones.
In a large bowl, toss the vegetables with 2 tbsp of olive oil and 1/2 tsp of salt. Pour the vegetables into the roasting pan, arranging them so most have a flat side down in the pan.
Roast for 15 minutes, stirring and turning the vegetables at 7 minutes.
Dry the washed greens to remove most of the water. Roughly chop the greens into bite-sized pieces, then toss them in the large bowl with the rest of the olive oil and the salt.
Pull the roasting pan out of the oven, turn and stir the vegetables again and then make a space for the greens. Spread out the greens in the space and return the pan to the oven.
Roast for 5 minutes more.