Preheat the oven to 425°F [220°C]. Rinse the lentils in a fine-mesh strainer under cold running water. Transfer to a medium saucepan and add enough water to cover by about 1 in [2.5 cm]. Bring to a rolling boil over medium-high heat, turn the heat to low, and simmer, uncovered, until tender but not mushy, 30 to 60 minutes. The cooking time will vary depending on how old the lentils are, so check them every 5 minutes after the first half hour. Drain through a fine-mesh strainer and set on a clean kitchen towel to absorb any remaining liquid.
While the lentils are cooking, roast the cauliflower and paneer: Break the cauliflower into bite-size florets and transfer to a roasting pan. Add the paneer. Season with the salt and pepper and drizzle with the olive oil, mixing to coat evenly. Roast, stirring occasionally, until the florets and paneer are crispy on the outside and feel tender when pierced with a skewer or knife, 20 to 25 minutes. Transfer to a large bowl and gently stir in the drained lentils and scallions. Taste and adjust the seasoning, if necessary. Drizzle with the dressing and serve warm or at room temperature. (Store the leftover salad in an airtight container in the refrigerator for up to 4 days.)