Preheat the oven to 400 degrees and line a large baking sheet with parchment paper and lightly oil the paper. Slice the cauliflower into 1/2 inch wide chunks and drizzle with half the olive oil. Toss the cauliflower with salt and pepper and then spread in an even layer on the parchment paper.
Roast for 20 minutes and then flip with a spatula and let roast for another 5 minutes. Transer the cauliflower to a serving dish and roast the almonds for 5 minutes or until lightly toasted, careful to avoid burning.
Grate the lemon for approximately 1 tsp of zest and squeeze the juice into a mixing bowl. Add the remaining olive oil and mix together well with the chopped mint. Mix the almonds, cauliflower and pesto together and serve.