Preheat the oven to 425°F: When the oven reaches 425°F you should notice the air feels noticeably hot as you open the door and the racks radiate warmth. This high heat is essential for rapid caramelization, producing golden brown edges rather than pale, steamed surfaces. Preheating fully avoids uneven cooking. A common mistake is placing vegetables into an oven that has not fully heated, which leads to longer cook times and less browning. Use an oven thermometer if your oven runs cool.
Toss the new potatoes, carrots, parsnips, and red onion with oil and seasoning: As you toss, feel the vegetable pieces take on a glossy sheen from the extra virgin olive oil . The seasonings should coat each surface so the aroma of oregano and lemon pepper becomes noticeable. This oil coating encourages Maillard reaction, giving the vegetables a sweet roasted smell. Avoid overcrowding the bowl while tossing, because uneven coating leads to patchy browning.
Spread the mixture evenly on a baking sheet and roast for 25 minutes: Arranging the vegetables in a single layer ensures hot air circulates and edges crisp. After ten to fifteen minutes you will start to hear gentle sizzling and smell sweet caramel notes. The visual cue to watch for is developing golden patches on the exposed surfaces. A frequent error is packing the tray too tightly, which traps steam and prevents the crisp texture you want.
Flip the vegetables and roast for 10 more minutes, or until everything is golden brown: When you turn the pieces, they should release readily from the pan and reveal deepening golden brown caramelization. The second roast helps even out color and finishes softening the centers to a tender bite. Listen for renewed sizzle as moisture escapes. If pieces look pale after the full time, leave them a bit longer, checking every five minutes so they do not burn.
Meanwhile, mix together the dressing ingredients until smooth: Whisk the plain greek yogurt , extra virgin olive oil , lemon juice and zest, ground black pepper, and the small pinch of salt until the texture is glossy and emulsified. The dressing should smell bright and tangy, with a creamy texture that will cling to roasted surfaces. If it is too thick, thin with a touch of water. A common slip is adding too much salt early, so taste and adjust near the end.
Remove the roasted vegetables from the oven and let cool: As the vegetables rest, they continue to release steam and mellow in flavor. Cooling for a few minutes prevents the arugula from wilting and helps the dressing adhere rather than run off. The residual warmth is perfect for slightly softening the feta cheese without melting it. If you toss immediately while piping hot, the greens will collapse and textures will be lost.
Toss together the cooled vegetables, arugula, cashews, feta, and dressing and serve!: When combining, you should hear a gentle rustle from the arugula and notice the creamy dressing lightly coating each root piece. The contrast of warm roasted vegetables against cool greens and creamy feta cheese is delightful. Toss gently to keep the cashews intact and the leaves fresh. Overmixing can bruise the greens and break up the cheese, so fold carefully until everything is just combined.