Preheat the oven to 425°. Place the mixed seeds into a small skillet and toast over medium to low heat. Set aside to cool.
Cut the carrots lengthwise and place in a large bowl. Add the cumin, paprika, garlic, thyme, lemon and orange. Drizzle on half of the olive oil and all of the red wine vinegar. Toss well to coat, place on heavy baking sheet and roast until the carrots begin to caramelize but are still crunchy. Remove from the oven and let cool.
Squeeze the lemon and orange juice into a bowl along with all the pan juices. Slowly drizzle in the remaining olive oil and whisk constantly until emulsified for the dressing. Peel and slice the avocado and squeeze the lemon wedge on top of it to prevent browning.
Return the carrots to the bowl, along with the salad greens and red onion, and toss with the dressing. Place on a serving platter or on individual plates, arrange several pieces of avocado amongst the carrots and greens, drizzle with the crema and sprinkle with the seeds.